UC-NRLF 


SB    7M    E3D 


ing 


Grieves 


MILITARY  SKETCHING 

AND 

MAP  READING 

BY 
CAPT.  LOREN  C.  GRIEVES 

INFANTRY 


SECOND  EDITION 


WASHINGTON 

UNITED  STATES  INFANTRY  ASSOCIATION 
1917 


Copyright   1917 
By  Capt.  Loren  C.  Grieves 


TABLE   OF   CONTENTS 


INTRODUCTION 
PART  I.— MAP  READING 
LESSON  I 

Page 

Length  of  Pace  or  Stride 5-6 

LESSON  II 
Individual  Scale  of  Paces  or  Strides. 7-13 

LESSON  III 
Solution  of  Scale  Problems 14-16 

LESSON  IV 
Miscellaneous  Scale  Problems 17-18 

LESSON  V 
Orientation,  Distance  and  Direction 19-27 

LESSON  VI 
Conventional  Signs 28-35 

LESSON  VII 
Relief  Maps 36-42 

LESSON  VIII 
Method  of  Determining  Difference  of  Elevation    .    43-48 

LESSON  IX 
Exercises  in  Contouring 49-52 

LESSON  X 
Visibility 53-56 

PART  II.— MILITARY  SKETCHING 

LESSON  XI 
Flat  Sketch 62-71 

LESSON  XII 
Road  Sketch. 72-76 

LESSON  XIII 
Position  and  Outpost  Sketches 77-82 

LESSON  XIV 
Place  Sketch 83-85 

LESSON  XV 
Miscellaneous 86-90 

APPENDIX 
Suggestions  for  Training  Camps 91-95 


3f>2094 


PREFACE 

In  writing  this  book  an  effort  has  been  made  to  produce 
a  text-book  on  Military  Sketching  and  Map  Reading 
meeting  the  requirements  of  the  curriculum  prescribed 
for  educational  institutions  operating  under  the  pro- 
visions of  the  War  Department,  also  to  meet  the  require- 
ments prescribed  in  the  examination  of  candidates  for 
commissions  in  the  Regular  Army  and  the  Reserve 
Officer's  Training  Corps,  and  to  provide  a  suitable  course 
for  the  officers  of  the  National  Guard,  and  thus  stand- 
ardize the  instruction  throughout  the  service.  In  view 
of  the  above,  attention  is  invited  to  War  Department 
orders  prescribing  text-books. 

It  has  been  the  aim  to  produce  a  suitable  text-book 
at  the  minimum  price,  free  from  all  extraneous  matter 
and  yet  completely  fulfilling  the  requirements. 

The  author  acknowledges  with  thanks  the  valuable 
assistance  rendered  by  Captain  A.  W.  Bjornstad  in 
co-ordinating  the  subject  matter  of  the  text  to  meet  the 
requirements  of  the  various  branches  of  the  military 
establishment. 


INTRODUCTION 

The  first  duty  of  the  instructor  is  to  eradicate  from 
the  mind  of  the  student  the  mistaken  idea  of  many  that 
this  is  a  difficult  subject.  Many  have  the  idea  that  one 
must  possess  artistic  abilities  in  order  to  become  proficient. 
That  is  not  true.  Simply  master  the  basic  principles  and 
apply  them.  Some  may  be  able  to  turn  in  neater  and 
more  artistic  sketches  than  others,  but  the  reader  is 
looking  for  facts,  and,  if  the  facts  are  shown,  the  sketch 
answers  the  purpose. 

The  subject,  in  so  far  as  this  text  is  concerned,  is 
divided  into  two  parts.  Part  I  treats  of  Military  Map 
Reading,  or,  the  classification  of  maps;  the  natural  and 
artificial  objects  represented  on  the  map;  methods  of 
interpretation  and  military  uses  of  maps.  Part  II 
treats  of  Military  Topographical  Sketching,  or  the  means 
and  methods  employed  in  making  military  road  and  area 
sketches,  and  the  reports  pertaining  to  them. 

It  is  enjoined  upon  the  instructor  to  employ  the  means 
and  methods  suggested,  and  to  anticipate  the  require- 
ments of  each  lesson  as  to  equipment.  Large  classes 
may  be  instructed  successfully  by  one  instructor  if  the 
right  methods  are  pursued.  The  suggestions  given  in 
the  Appendix  which  pertains  to  training  camps  apply 
in  so  far  as  the  equipment  is  concerned  to  the  work  in 
organizations  and  educational  institutions. 


PART  I 
LESSON  I 

LENGTH  OF  PACE  OR  STRIDE 
Before  taking  up  the  subject  of  scales,  tike 


should  determine  the  length  of  his 

An  accurately  measu 
yards  should  be  selected.  A  thousand  yards  on  the 
target  range  wfll  answer  the  purpose,  or,  if  a  target 
range  is  not  available,  a  course  may  be  measured,  prefer- 
ably on  turf  rather  than  on  a  macadamized 
walk.  While  pacing,  one  should  take  an 
and  uniform  gait.  This  is  important  as  there  is  always  a 
tendency  on  the  part  of  the  beginner  to 
and  his  natural  gait  as  entirely  distinct, 
results  in  his  first  scale  of  paces  or  strides  being  too 
This  may  be  obviated  by  pacing  a 
several  times  (four  tunes  is  suggested),  first 
upon  the  student's  mind  the  necessity  of  taking  a  natural 
and  uniform  gait. 

Let  us  assume  that  each  student  has  paced  the 
four  rimer,  and  that  his  four  results 
1,000  yards  long  are: 

1118 
I]  • 
11*0 
1117 


To  determine  the  length  of  his  pace  in 


Before  computing  the  length  of  his 
should  present  his  results  of  pacing  to  the 
verification,  and,  if  any  wide 
dent  should  be  lequked  to  pace  the 

To  avoid  error  in  urn  mi,  the 


6  MILITARY  SKETCHING 

of  the  number  of  paces  by  making  a  mark  for  each  100 
paces.  A  pace  tally  may  be  used  if  available.  A  hand 
instrument  known  as  a  "Tallying  Register"  may  be  used 
in  recording  the  number  of  strides,  if  a  scale  of  strides  is 
desired. 

To  accurately  determine  the  length  of  pace  or  stride 
of  each  student,  without  doubt,  will  occupy  the  time  avail- 
able for  the  first  lesson,  and  the  construction  of  scales  will 
be  taken  up  in  the  next  lesson. 

REVIEW 

Explain,  as  to  a  beginner,  exactly  how  to  determine  the 
length  of  one's  pace  or  stride. 


LESSON  II 

INDIVIDUAL    SCALE    OF    PACES    OR    STRIDES, 
READING  SCALES 

Having  determined  the  length  of  our  pace  or  stride, 
let  us  now  consider  the  subject  of  scales  of  maps.  It  is 
very  clear  that  the  ground  and  all  of  the  objects  upon  it 
cannot  be  represented  as  large  on  the  map  as  they  ac- 
tually are.  They  must  be  reduced  in  size.  In  other 
words,  any  distance  on  the  map  is  a  certain  fixed  part  of 
the  corresponding  distance  on  the  ground,  and  this  re- 
lation between  map  distance  and  ground  distance  is  called 
the  scale  of  the  map. 

The  scale  should  be  no  larger  than  is  necessary  to  bring 
out  all  of  the  required  details.  For  example,  it  has  been 
found  that  the  scale,  3  inches  =  1  mile  (meaning  that  3 
inches  on  the  map  represents  1  mile  on  the  ground), 
is  the  proper  scale  for  "Road  Sketches."  It  gives  just 
enough  room  to  insert  all  of  the  details  of  military  impor- 
tance, while,  if  we  were  to  use  the  scale,  1  inch  =  1  mile,  for 
"Road  Sketches,"  there  would  not  be  enough  room,  and 
by  using  the  scale  6  inches  =  1  mile,  we  would  burden  our- 
selves and  those  reading  the  map  with  an  unnecessary 
amount  of  paper. 

There  are  three  ways  in  which  the  scale  of  a  map  may  be 
represented. 

1st.  A  plain  statement,  as,  for  example,  3  inches  equals 
1  mile. 

2nd.  Represented  by  a  fraction.  To  determine  the 
fraction  representing  any  scale,  as  3  inches  =  1  mile,  let 
the  map  distance  be  the  numerator  and  the  ground  dis- 
tance the  denominator,  BOTH  TERMS  OF  THE 
FRACTION  BEING  OF  THE  SAME  DENOMINA- 
TION, then  reduce  the  fraction  so  that  the  numerator 
will  be  unity,  as,  for  example: 

3  inches  on  map  _     3  inches  1      _  Representative  Fraction 

1  mile  on  ground "63360  inches" 21120"     (abbreviated  R.  F.) 


8  MILITARY  SKETCHING 

3rd.  Graphically,  in  which  the  scale  is  actually  repre- 
sented on  the  map,  or  on  a  ruler  by  a  line  divided  into 
equal  parts,  each  division  being  marked  by  the  distance 
which  it  represents  on  the  ground. 

There  are  two  kinds  of  graphical  scales:  one  for  mak- 
ing the  map,  called  a  working  scale,  and  one  for  reading 
the  map,  called  a  reading  scale.  If  the  same  units  of 
measure  were  used  for  both  map  making  and  map  read- 
ing, one  scale  would  answer  for  both  purposes;  but  this 
is  seldom  the  case,  as  we  may  obtain  our  distances  in 
terms  of  paces  or  strides  of  various  lengths  depending  upon 
the  individual,  while  the  party  reading  the  map  neces- 
sarily must  have  the  distances  expressed  in  terms  of  well- 
known  units  such  as  yards  or  miles. 

To  CONSTRUCT  A  WORKING  SCALE  OF  PACES 
Let  us  assume  that  a  student  has  paced  a  course  of  a 
thousand  yards  four  times  with  the  following  results: 

1st  result,  1118  paces. 
2nd  result,  1109  paces. 
3rd  result,  1120  paces. 
4th  result,  1117  paces. 

He  wishes  to  construct  a  working  scale,  3  inches  on  the 
scale  representing  1  mile  on  the  ground.  To  do  so  he 
should  proceed  as  follows: 

1st.   Find  the  length  of  his  pace. 

2nd.  Find- how  many  of  his  paces  will  be  represented  by 
one  inch  on  the  map. 

3rd.   Find  the  length  in  inches  of  his  working  scale. 
4th.  Construct  the  scale. 

1st 

To  FIND  THE  LENGTH  OF  His  PACE 
(See  Lesson  I) 

2nd 

To  FIND  How  MANY  OF  His  PACES  WILL  BE  REPRE- 
SENTED BY  ONE  INCH  ON  THE  MAP 

3  inches  on  the  map  =  63360  inches  on  the  ground. 
1  inch,  on  the  map  =  21 120  inches  on  the  ground. 
21,120^32  =  660  of  his  paces. 


INDIVIDUAL  SCALE  OF  PACES  OR  STRIDES  9 

3rd 

To    FIND    THE   LENGTH   IN   INCHES    OF   A    CONVENIENT 
WORKING  SCALE  REPRESENTING  SAY  2,400  PACES 

•  660  paces  =  1  inch. 
2,400-^660  =  3.63  inches,  length  of  scale. 

To  CONSTRUCT  THE  SCALE 

Lay  off  the  line  AB  (Fig.  1),  3.63  inches  long,  which 
represents  2,400  paces.  Divide  this  line  into  24  equal 
divisions  representing  100  paces  each.  Divide  the  first 
one  of  these  divisions  on  the  left  into  five  equal  parts  repre- 
senting 20  paces  each.  Transfer  these  divisions  to  a  suit- 
able straight-edge  ruler  and  the  working  scale  is  com- 
pleted. Working  scales  of  1",  6",  and  12"  to  the  mile 
may  be  constructed  in  a  similar  manner,  also  working 
scales  of  strides. 

To  divide  the  line  AB  (Fig.  1)  into  24  equal  divisions, 
lay  off  any  line  AC  that  can  be  conveniently  divided  into 
24  equal  parts.  Draw  a  straight  line  connecting  B  and 
(7,  then  draw  lines  parallel  to  BC  as  shown  in  the  figure. 
These  lines  will  divide  AB  into  24  equal  divisions  of  100 
paces  each.  Use  the  same  method  for  the  divisions  repre- 
senting 20  paces. 

The  ruler  shown  in  Fig.  2  is  the  most  suitable  for  sketch- 
ing. It  is  made  of  a  triangular,  straight-edged  piece  of 
hard  wood.  A  hole  3/8  inch  in  diameter  and  2  inches 
deep  may  be  bored  into  each  end  of  the  ruler  and  filled 
with  lead  to  give  it  weight.  This  form  of  ruler  furnishes 
a  well-defined  sighting  line,  and  is  the  most  convenient 
of  any  working  scale  yet  devised.  The  material  may  be 
obtained  by  the  instructor  and  cut  into  6-inch  strips, 
and,  if  practicable,  filled  with  lead;  or  they  may  be  obtained 
at  a  nominal  price  from  the  Book  Department,  Army 
Service  Schools,  providing  the  Book  Department  is  fur- 
nished with  the  necessary  data  as  to  the  various  lengths 
of  paces  or  strides  desired. 

After  determining  the  length  of  your  pace  or  stride, 
the  working  scale  may  be  transferred  to  the  ruler  directly 


10 


MILITARY  SKETCHING 


fa 


INDIVIDUAL  SCALE  OF  PACES  OR  STRIDES  11 

from  the  consolidated  scales  shown  in  Fig.  3  by  placing 
the  edge  of  the  ruler  on  the  proper  line  or  interpolating 
between  lines.  This  is  sometimes  found  to  be  more 
practicable  with  certain  non-commissioned  officers  than 
attempting  to  require  them  to  solve  the  problems. 

i  i  i  i  i  i  i  i  i  i  i  i  i  i  i  \  \  \  \  \  \  \  \  n 

2  4  6  8  ID  12  li  16  18  20  23          3AOO 

3  in.      iTOJ.  32in.Pace 

FIG.  2 

To  CONSTRUCT  A  READING  SCALE  OF  YARDS 

After  a  sketch  has  been  completed,  you  wish  to  place 
upon  the  sketch  a  reading  scale  of  yards  so  that  any 
other  person  may  be  able  to  read  distances  correctly 
from  your  sketch. 

Assume  that  the. scale  of  your  sketch  is  3  inches  =  1 
mile,  or  1  inch  =  21120  inches  =  596.66  yards.  Say  that 
you  desire  a  reading  scale  that  reads  to  3,000  yards. 

3,000^596.66  =  5.11  inches,  the  length  of  your  scale. 

With  a  box- wood  scale,  lay  off  a  line  5.11  inches  long, 
and  by  the  method  explained  in  Fig.  1  divide  it  into  30 
equal  parts,  or  any  other  number  of  equal  parts,  and  your 
reading  scale  of  yards  is  completed. 

REVIEW 

1.  What  is  meant  by  the  scale  of  a  map? 

2.  In  what  three  ways  may  scales  be  represented? 

3.  Six  inches  on  a  certain  map  represents  1  mile  on  the 
ground.     Represent  the  scale  of  this  map  by  the  three 
methods. 

4.  Construct  a  working  scale  of  paces  for  your  own  use 
for  making  a  map  on  a  scale  3"  =  1  mile,  also  a  working 
scale  of  paces  for  your  own  use  for  making  a  map  on  a 
scale  of  6"=  1  mile. 

5.  How   may  the  above   working  scales  be  converted 
into  working  scales  of  strides? 


MILITARY  SKETCHING 


1:21120  3   lN.=1Mi. 

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10      12      14      16      18     20    22    ZA   26     28    3000 


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47 


^lOO      6        i        2       i      *       5       6       7      8       §      ib       .'I      12      IS     14     1500 
6m--lmi.  0  123456  700    Paces 

1in.«lmL  03       6      9      12     15     18     21     24    27    30    33    36    39     4200  Paces 


FIG.  3 


INDIVIDUAL  SCALE  OF  PACES  OR  STRIDES 


13 


SCALE    H2M2O  3iN.=  iMi. 


7       8       9       10      II  13      14      1500 


00  Paces 
500  Paces 
27       3000  Paces 


FIG.  3 


LESSON  III 
SOLUTION  OF  SCALE  PROBLEMS 

PROBLEM  No.   1 

Scale  of  minutes  to  be  used  by  mounted  sketcher. 

A  sketcher's  horse  trots  1  mile  in  8  minutes.      Construct 

a  scale  of  minutes  for  an  R.  F.  of  ~,  ,  ,-. 

xllsJU 

Solution: 

8  minutes  =  63360  inches. 

1  minute  =  7920  inches. 

1  inch  on  map  =  21  120  inches  on  the  ground. 

21120       2 

2—  minutes  to  cover  one  inch  on  map. 


Let  us  construct  a  scale  6"  long. 

a 

2—  X6=  16  minutes  to  cover  6  inches. 

D 

Construct  the  scale  by  dividing  a  line  6  inches  long  into 
16  equal  parts,  each  part  representing  the  distance 
traveled  in  one  minute.  Divide  the  space  on  the  left 
into  4  equal  parts  giving  the  distance  traveled  in  a  quarter 
of  a  minute. 

PROBLEM  No.  2 
Foreign  Maps 

You  are  given  a  foreign  map,  scale,  1  centimeter  =  1 
Kilometer. 

(a)   Required,  the  R.  F. 

Solution: 

Simply  reduce  1  Kilometer  to  centimeters,  and  we  have  the  R.  F. 


100,000 

(b)  How  many  inches  to  the  mile  in  this  scale? 

RULE:  To  determine  the  number  of  inches  to  the  mile 
of  any  R.  F.,  divide  63360  by  the  denominator  of  the 
R.  F. 

14 


SOLUTION  OF  SCALE  PROBLEMS  15 

PROBLEM  No.  3 
Foreign  Maps 

You  are  given  a  foreign  map  with  a  reading  scale 
only.  By  measuring  the  reading  scale,  you  find  that 
1  Kilometer  =  .92  inch.  What  is  the  R.  F.  of  the  map? 

Solution: 

1  KM.  =  1,000  meters. 
1  meter  =  39. 37  inches. 
1  KM.  =  39370  inches. 
.92  inch  on  map  =  39370  inches  on  the  ground. 

39370  =  42793  =  R'  F' 

PROBLEM  No.  4 

Map  of  Local  Terrain  with  no  Scale 
To  Determine  the  R.  F. 

Measure  the  distance  between  two  points  on  the  ground 
that  are  located  on  the  map,  then  measure  the  map 
distance  between  the  two  points.  Let  the  map  distance 
be  the  numerator  and  the  ground  distance  the  denom- 
inator, BOTH  BEING  REPRESENTED  IN  THE 
SAME  DENOMINATION.  Reduce  the  fraction  so 
that  the  numerator  is  unity  and  you  have  the  R.  F. 

PROBLEM  No.  5 

Relation  of  Scale  to  Area  of  Maps 
Rule 

To  change  the  area  of  a  map,  multiply  each  of  its 
linear  dimensions  by  the  square  root  of  the  change. 

Example: 

A  map  12"  by  20"  is  to  be  reduced  to  —  of   its  present  area, 


So  it  is  seen  that  6"xlO"  are  the  reduced  dimensions. 
Also,  a  map  12"x20"  is  to  be  enlarged  to  4  times  its 
present  area. 


16  MILITARY  SKETCHING 

Applying  the  same  rule,  we  find  that  the  new  dimen- 
sions are  24"x40". 

PROBLEM  No.   6 
Correction  of  Erroneous  Scales 

You  are  directed  to  make  a  road  sketch,  scale  3"  =  1 
mile.     You  use  a  working  scale  of  32"  paces.     Later  you 
find  that  your  pace  is  actually  30".      What  is  the  R.  F. 
of  the  sketch  actually  made? 
Solution: 

If  your  pace  had  actually  been  32"  long,  the  R.  F.,  of  course, 
would  have  been  .     The  result  of  your  shorter  pace  is  the  en- 

largement of  the  scale  of  the  map,  that  is,  a  R.  F.  with  a  smaller 

30          -          1 
denominator  by  — ,  making  the  proper  R.  F. 


LESSON  IV 
MISCELLANEOUS  SCALE  PROBLEMS 

1.  Construct  a  working  scale  of  paces  for  a  map  on  the 
scale  of  12"  =  1  mile,  110  paces  being  equal  to  100  yards. 

2.  A  sketcher's  horse  trots  a  mile  in  7  minutes.      Con- 
struct   a   scale    of    minutes    and    quarter    minutes   for   a 

R'Rof  10560' 

3.  A  foreign  map  is  reproduced  on  a  scale  of 


(a)    Construct  a  reading  scale  to  show  10  -miles  on  the 
map. 

(6)   Construct  a  reading  scale  to  show  10  Kilometers. 
(1  Meter  equals  39.37  inches.) 

4.  Your  pace  is  32"  long.      You  are  given  a   map  of 
local   terrain    which   has   no   scale.      Two   points   on   the 
ground   which   are  located   on   the   map   have   a   ground 
distance  of  4,000  of  your  paces.      The   map   distance  is 
6.3  inches.      What  is  the  R.  F.  of  the  map? 

5.  You  are  given  a  French  map  with  a  reading  scale 
only.      By    measuring    the   reading   scale,    you    find    that 
1  Kilometer  =  .76  inch.      What  is  the  R.  F.  of  the  map? 

6.  The  dimensions  of  a   map  with  a  R.   F.   of  — 


is  6"  by  8"; 

What  will  be  the  dimensions  of  the  map  of  a  R.  F.  of 

-^7T?     How  much  is  its  area  increased? 
10,560 

7.  You  are  directed  to  make  a  position  sketch,  scale 
6"  =  1    mile.     You   use   a    working   scale   of   64"   strides. 
Later  you  find  that  your  stride  is  actually  60".      What  is 
the  R.  F.  of  the  sketch  actually  made? 

8.  Draw  a  reading  scale  of  yards  for  a  map  15  by  18 
inches  to  show  an  area  of  6  square  miles. 

9.  Our    geological      maps    have    a    R.    F.    of    ^ 

17 


18  MILITARY  SKETCHING 

Construct  a  reading  scale  of  miles,  halves,  and  quarters. 
One  inch  on  our  geological  maps  equals  how  many 
yards? 

10.  Compare  the  scales  of  various  maps,  such  as  our 
geological  maps,  maps  of  your  city,  geographical  maps 
of  states,  county  maps,  construction  maps,  etc. 

Always  note  the  scale  of  a  map  before  attempting  to 
read  the  map. 


LESSON  V 
ORIENTATION,   DISTANCE,   AND  DIRECTION 

In  the  practical  use  of  a  map  in  the  field,  the  next  step, 
after  determining  its  scale,  is  to  "Orient"  the  map. 

In  order  to  compare  the  map  with  the  ground  that  it 
represents,  we  must  first  see  that  the  directions  on  the 
map  and  on  the  ground  coincide.  This  is  called  "Orient- 
ing the  map." 

All  complete  maps  have  both  the  magnetic  and  true 
meridian  indicated.  The  true  meridian  is  a  straight  line 
joining  the  observer's  position  and  the  north  pole  of  the 
earth.  The  magnetic  meridian  is  a  straight  line  that 
coincides  in  direction  with  the  magnetic  needle  of  the 
compass  at  the  observer's  position.  The  directions  of  the 
needle  at  different  places  on  the  earth's  surface  converge 
approximately  toward  the  magnetic  poles  of  the  earth. 
These  poles  do  not  coincide  with  the  poles  of  the  earth's 
axis,  and  therefore  the  magnetic  and  true  meridians  do 
not  generally  coincide. 

The  angle  between  the  magnetic  and  true  meridian  at 
any  place  is  called  the  "Declination  of  the  needle"  for 
that  place. 

There  is  a  certain  irregular  line  on  the  earth's  surface 
at  all  points  of  which  the  true  and  magnetic  meridians 
coincide  and  the  declination  is  zero.  This  line  is  called 
the  "agonic"  line.  In  the  United  States  it  passes  in  a 
southeasterly  direction  from  Michigan  through  inter- 
vening states  to  South  Carolina.  The  agonic  line  is  not 
permanent,  but  is  slowly  moving  westward.  At  all 
points  in  the  United  States  east  of  the  agonic  line,  the 
north  end  of  the  needle  inclines  to  the  west  of  the  true 
meridian.  To  the  west  of  the  agonic  line  the  needle  in- 
clines to  the  east  of  the  true  meridian. 

Isogonic  lines  are  lines  joining  points  of  the  same 
declination  of  the  needle.  As  the  agonic  and  isogonic 
lines  are  gradually  changing,  maps  should  always  have 
the  true  as  well  as  the  magnetic  meridian  indicated. 

19 


20  MILITARY  SKETCHING 

There  are  a  few  simple  methods  of  determining  the  true 
meridian  (true  north  and  south  line),  with  a  degree  of  ac- 
curacy sufficient  for  military  sketching  and  map  reading. 
For  an  accurate  instrumental  survey,  an  observation  on 
Polaris  (North  Star)  should  be  taken.  This  is  not  in- 
cluded in  the  text,  as  it  properly  comes  under  the  head 
of  advanced  surveying. 

First  Method 

By  means  of  the  North  Star. — Without  instruments,  it 
can  be  determined  approximately  by  placing  two  cords, 
with  weights  attached,  in  line  with  the  star.  The  cords 
should  be  about  12  feet  apart,  and  to  see  the  forward 
one,  it  will  be  necessary  to  throw  a  light  upon  it.  This 
line  can  readily  be  prolonged  by  daylight. 

Second  Method 

By  aid  of  the  sun  and  plumb-bob  (see  Fig.  4). — On  a 
level  piece  of  ground  lean  a  pole  toward  the  north,  and 
rest  it  in  a  crotch  made  by  two  sticks  as  shown.  Sus- 
pend a  weight  from  the  end  of  the  pole  so  that  it  nearly 
touches  the  ground;  then,  about  an  hour  before  noon,  at- 
tach a  string  to  a  peg  driven  directly  under  the  weight, 
and,  with  a  sharpened  stick  attached  to  the  other  end  of 
the  string,  describe  an  arc  with  a  radius  equal  to  the  dis- 
tance from  the  peg  to  the  shadow  of  the  tip  of  the  pole. 
Drive  a  peg  on  the  arc  where  the  shadow  of  the  tip  of  the 
pole  rested.  About  an  hour  after  noon  watch  the  shadow 
of  the  tip  as  it  approaches  the  eastern  side  of  the  arc,  and 
drive  another  peg  where  it  crosses.  By  means  of  a 
tape  or  string,  find  the  middle  point  of  the  straight  line 
joining  the  last  two  pegs  mentioned.  A  straight  line 
joining  this  middle  point  and  the  peg  under  the  weight  will 
be  in  the  true  meridian.  Place  a  pole  about  a  hundred 
yards  in  prolongation  of  this  line,  and  with  the  compass 
sight  back  on  the  tip  of  the  inclined  pole,  and  the  declina- 
tion will  be  obtained. 


ORIENTATION,  DISTANCE,  AND  DIRECTION 


Third  Method 

By  aid  of  the  watch  and  sun. — Lay  the  watch  on  some 
level  surface  and  revolve  it  until  the  hour  hand  points  di- 
rectly under  the  sun.  Then  by  reference  to  the  divisions 


FIG.  4 

on  the  dial,  determine  a  point  on  it  midway  between  the 
hour  hand  and  twelve  o'clock.  A  line  through  this  point 
and  the  pivot  of  the  hands  will  be  approximately  in  the 
true  meridian.  (See  Fig.  5.) 

The  operation  of  pointing  the  hour  hand  directly  under 
the  sun  is  made  easy  by  casting  the  shadow  of  a  vertical 


FIG.  5 


straight  stick  across  the  face  of  the  watch  ajid  then  bring- 
ing the  hour  hand  into  this  shadow. 

The  watch  method  will  not  answer  during  certain  sea- 
sons in  the  tropics  when  the  sun  passes  directly  overhead. 


22  MILITARY  SKETCHING 

There  is  also  another  slight  error  due  to  the  fact  that  in 
some  sections  there  is  a  difference  of  half  an  hour  be- 
tween standard  and  sun  time. 

ORIENTING  THE  MAP 

As  heretofore  stated,  all  complete  maps  have  both  the 
true  and  the  magnetic  meridian  indicated.  However,  it 
is  assumed  that  you  have  found  the  declination  of  the 
needle  for  your  particular  locality,  so,  if  either  the  true 
or  the  magnetic  meridian  be  given,  the  other  can  be  readily 
determined. 

First  Method 

When  the  map  has  the  magnetic  meridian  marked  on  it: 
Place  the  compass  on  the  map,  so  that  the  needle  pivot 
rests  on  the  magnetic  meridian;  revolve  the  map  until  the 
north  end  of  the  needle  and  the  magnetic  meridian  point 
in  the  same  direction,  whereupon  the  map  is  oriented. 

Suppose  that  only  the  true  meridian  is  given  on  the  map. 
Knowing  the  declination  of  the  needle,  construct  a  mag-, 
netic  meridian  and  proceed  as  above. 

Second  Method 

Suppose  that  neither  the  magnetic  nor  the  true  meri- 
dian is  indicated  on  the  map. 

(a)  Take  position  on  the  ground  corresponding  to 
some  point  on  the  map.  Identify  another  point  on  the 
map  that  you  can  see  on  the  ground.  Join  the  two  map 
positions  by  a  straight  line.  Hold  the  map  so  that  this 
line  points  toward  the  distant  point  seen  on  the  ground, 
whereupon  the  map  is  oriented. 

(6)  Place  yourself  on  the  line  of  any  two  points  visible 
on  the  ground  and  plotted  on  the  map,  rotate  the  map 
until  the  line  joining  the  two  points  on  the  map  points 
towards  the  two  points  on  the  ground,  whereupon  the 
map  is  oriented. 

(c)  Observation,  co-ordinating  map  with  the  various 
visible  terrain  features. 


ORIENTATION,  DISTANCE,  AND  DIRECTION  23 

To  LOCATE  YOUR  MAP  POSITION 
First  Method 

After  the  map  is  oriented  by  the  compass: 
Sight  along  the  rule  at  an  object  on  the  ground  at  the 
same  time  keeping  the  rule  on  the  plotted  position  of  this 
object  on  the  map.  Draw  a  line  toward  your  body. 
Find  another  point  on  the  ground  that  is  plotted  on  the 
map  and  repeat  the  process.  The  intersection  of  the  two 
lines  is  your  map  position.  The  two  points  selected 
should  be  so  located  that  the  angle  formed  at  the  inter- 
section of  the  lines  should  be  not  less  than  30  degrees  nor 
greater  than  120  degrees,  otherwise  the  two  intersecting 
lines  are  so  nearly  parallel  that  it  is  difficult  to  locate  the 
exact  point  of  intersection. 

Second  Method 

If  "the  map  has  been  oriented  by  means  of  a  straight  line 
drawn  between  two  map  points,  then  it  will  be  necessary 
to  draw  but  one  line  from  the  object  on  the  ground,  and  the 
intersection  of  this  line  with  the  line  already  on  the  map 
will  be  your  location  on  the  map. 

Third  Method 
Observation. 

MAP  DISTANCES 

Knowing  the  scale  of  our  map  and  having  oriented  it, 
we  should  now  be  able  to  determine  from  the  map  the 
distance  between  objects  on  the  ground  and  the  direction 
of  one  from  another. 

We  will  first  consider  converting  map  distance  into 
ground  distance.  Every  complete  map  has  a  reading 
scale  of  some  well-known  unit  as  yards  or  miles,  so  all 
that  is  necessary  to  determine  the  ground  distance  be- 
tween points  on  the  map  is  to  apply  the  reading  scale  to 
the  map  distance  or  the  map  distance  to  the  reading  scale. 

There  are  several  simple  methods  of  taking  distances 
from  the  map: 


24  MILITARY  SKETCHING 

First  Method 

v  ' 

Suppose  that  you  have  no  reading  scale  except  the  one 
printed  on  the  map.  If  such  is  the  case,  apply  a  piece  of 
straight-edged  paper  to  the  distance  between  the  two 
points  to  be  measured.  Mark  the  distance  on  the  paper, 
and  apply  the  paper  to  the  reading  scale  of  the  map,  or 
copy  off  the  reading  scale  on  a  piece  of  paper  and  apply 
the  paper  to  the  map. 

Second  Method 

A  scale  of  inches  may  be  applied  to  the  distance  be- 
tween the  two  points  to  be  measured,  then  multiply  the 
number  of  inches  between  the  two  points  by  the  number 
of  miles  per  inch  given  on  the  map.  (Caution:  do  not 
confuse  the  terms— "miles  per  inch,"  and  "inches  per 
mile.") 

Third  Method 

The  Geological  Survey  maps  made  on  a  scale  of  1-62,500 
are  much  used  by  the  army,  but  as  there  is  a  difference  of 
but  about  1  per  cent  between  these  maps  and  maps  made 
on  the  scale  of  1-inch  equals  Imile,  the  1-inch  reading  scale 
is  sufficiently  accurate  for  most  purposes. 

Fourth  Method 

It  is  often  necessary  to  take  off  distances  from  the  map 
in  terms  of  one's  paces  or  strides.  To  do  so,  simply 
apply  your  scale  of  paces  for  1,  3,  or  6  inches  to  the  mile  to 
maps  of  those  scales,  and  for  maps  of  2,  4,  or  5,  or  any 
other  whole  number  not  represented  on  your  scale  of  paces, 
apply  your  1-inch  scale  of  paces  and  divide  the  result  by 
two,  four,  or  five  as  the  case  may  be. 

Fifth  Method 

Map  Measurer. — A  small  instrument  so  constructed  that 
it  may  be  rolled  over  the  surface  of  the  map,  and  will 
record  on  a  dial  the  distance  passed  over.  Complete 
instructions  for  its  use  are  given  with  each  instrument, 


ORIENTATION,  DISTANCE,  AND  DIRECTION  25 

This  instrument  is  especially  valuable  for  use  in  map  prob- 
lems and  war  games. 

MAP  DIRECTIONS 

As  the  captain  consults  his  chart  and  compass  in  guid- 
ing his  ship,  so  must  the  soldier  consult  his  map  and  com- 
pass in  traveling  through  unknown  regions. 

The  usual  style  of  box  compass  or  other  small  compasses 
has  the  four  cardinal  points,  N.,  E.,  S.,  and  W.  (North, 
East,  South,  and  West),  marked  on  its  surface,  and  a 
circle  graduated  in  degrees  reading  zero,  clockwise  around 
to  360  degrees,  beginning  and  ending  at  N.  In  order  to 
travel  by  the  compass,  one  must  be  able  to  convert  map 
directions  into  compass  directions;  in  other  words,  we 
must  be  able  to  determine  the  MAGNETIC  AZIMUTH 
of  any  line. 

By  the  Magnetic  Azimuth  of  a  line  is  meant  the  hori- 
zontal angle  that  the  line  makes  with  the  compass  needle 
measuring  from  the  north  point  clockwise  around  the 
circle.  The  True  Azimuth  is  measured  in  the  same  direc- 
tion from  the  north  point  of  the  True  Meridian  (true 
north  and  south  line). 

A  protractor  is  an  instrument  for  measuring  and 
plotting  angles.  A  protractor  is  usually  so  graduated 
that  it  is  laid  on  the  east  side  of  the  meridian  through 
the  plotted  position  for  plotting  angles  from  zero  to 
180  degrees,  and  from  180  degrees  to  360  degrees  the 
protractor  is  placed  on  the  west  side  of  the  meridian. 

To  illustrate — you  are  at  the  point  A,  Fig.  6,  and  you 
wish  to  obtain  the  magnetic  azimuth  of  the  line  AB. 
Draw  a  line  AC  through  A  parallel  to  the  magnetic  north 
and  south  line.  Lay  your  protractor  along  AC,  the 
center  of  the  protractor  at  A.  (The  center  of  the  pro- 
tractor is  indicated  by  an  arrow  point.)  Read  the  number 
of  degrees  between  AC  and  AB.  It  is  found  to  be  63 
degrees,  which  is  the  magnetic  azimuth  of  the  line  AB. 

Then  suppose  that  you  are  at  A,  and  wish  to  proceed 
in  the  direction  of  B.  Simply  hold  the  compass  so  that 


c. 


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Fie.  6 


ORIENTATION,  DISTANCE,  AND  DIRECTION  27 

the  needle  is  at  N,  then  follow  in  prolongation  of  a  line 
drawn  through  the  pivot  of  the  needle  and  the  63-degree 
point.  The  course  is  kept  by  an  occasional  reference  to 
the  compass  which  is  held  in  front  of  you  or  placed  upon 
the  ground. 

Maps  of  various  scales  should  be  issued  to  members  of 
the  class,  who  should  determine  the  distance  in  terms  of 
yards,  miles,  or  paces,  and  the  magnetic  azimuth  between 
designated  points  in  accordance  with  instructions  given 
in  this  lesson. 

QUESTIONS  FOR  REVIEW 

1.  What  is   meant  by   the   expression,   "orienting   the 
map?" 

2.  What  is  meant  by  the  true  and  magnetic  meridians? 

3.  What  is  meant  by  the  declination  of  the  needle? 

4.  What  is  the  agonic  line? 

5.  What  are  isogonic  lines? 

6.  What  is  the  declination  of  the  needle  to  the  east  of 
the  agonic  line?     To  the  west? 

7.  Describe    three    methods    of    determining    approxi- 
mately the  true  meridian. 

8.  Describe  two  methods  of  orienting  the  map. 

9.  Describe  two  methods  of  locating  your  position  on 
the  map. 

10.  Describe  the  methods  of  scaling  distances  on  the  map. 

11.  What  is  meant  by  the  magnetic  azimuth  of  a  line? 
The  true  azimuth  of  a  line? 

12.  What  is  a  protractor? 

13.  Describe  the  use  of  the  protractor  in  determining 
the  true  and  magnetic  azimuth  of  lines. 

14.  Practical    problems    in    determining    distance    and 
azimuth  of  points  on  the  map  should  be  given  the  class. 


LESSON  VI 
CONVENTIONAL  SIGNS 

Having  learned  how  to  read  distances  and  directions 
on  the  map,  we  will  now  consider  the  many  natural  and 
artificial  ground  features  of  importance  and  the  method 
of  representing  them  on  the  map. 

In  order  that  all  may  be  able  to  read  the  map  when 
completed,  we  must  have  some  fixed  method  of  repre- 
senting these  ground  features.  With  this  in  view  the 
United  States  Geographic  Board  adopted,  in  1912,  a 
system  of  conventional  signs  for  the  use  of  all  map- 
making  departments  of  the  government.  At  the  close 
of  the  lesson  are  those  that  pertain  to  the  work  to  be 
covered  by  this  book.  Members  of  the  class  should  be 
required  to  reproduce  these  signs  as  neatly  as  possible, 
and  this  lesson  should  be  devoted  to  that  purpose. 

The  instructor  should  superintend  and  criticise  the 
work;  especially  should  he  avoid  the  usual  tendency  cf 
making  the  signs  too  large.  The  ability  to  neatly 
reproduce  these  conventional  signs  should  be  included 
in  the  examination  over  this  subject.  When  you  find 
some  idle  moments  with  a  pencil  and  paper  at  hand,  your 
time  may  be  profitably  employed  by  practicing  the  con- 
struction of  conventional  signs. 

Just  a  few  words  about  pencils  would  not  be  amiss  at 
this  particular  point. 

The  best  for  plotting  are  the  hard  kinds  corresponding 
to  Faber's  Siberian  HHHH  and  HHHHHH,  especially 
for  drawing  fine  lines  and  making  points.  For  most 
kinds  of  work,  a  sharp-pointed  pencil  is  used.  .  For 
drawing  long,  straight  lines,  a  chisel-pointed  pencil 
should  be  used  to  produce  a  line  of  uniform  breadth. 
For  sketching  and  filling  in  conventional  signs,  softer 
pencils  are  preferable,  such  as  correspond  to  Faber's  HB. 
To  keep  the  point  always  in  good  condition  one  should 
have  a  piece  of  fine  sandpaper  at  hand  for  that  purpose, 


CONVENTIONAL  SIGNS 


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»        s 

"§            -I'll 

i 

'l 

0 

1 

1 

C 

• 

.   | 

> 

i 

•    § 

0 

Mortar  Batte 

K 

2       0 

fe  1  1 

u,      a:      o 

•\ 

1 

u                 t»o         :        3 
c           •     *         !       J 

^       ,«o        Uj        "2        t> 

1  .s  1  ! 

1  i  1  1 

Controlled  mi 

3 


CONVENTIONAL  SIGNS  35 

being  careful  to  remove  any  lead  dust  from  the  point 
before  using.  Much  more  depends  upon  the  proper 
sharpening  of  a  pencil,  and  afterwards  keeping  it  so, 
than  is  commonly  supposed. 

Most  drawings  to  be  inked  are  first  constructed  in 
pencil,  the  lines  being  made  with  as  little  pressure  and  as 
fine  as  is  possible  to  show  distinctly. 


LESSON   VII 
RELIEF  MAPS 

We  have  learned  how  to  determine  from  the  map  the 
horizontal  distances  between  points  on  the  ground,  the 
direction  of  one  point  from  another,  and  the  conventional 
signs  representing  the  various  terrain  features,  but,  in 
order  to  have  a  better  knowledge  of  the  earth's  surface, 
we  must  have  some  method  of  rapidly  determining  eleva- 
tions. In  other  words,  we  must  know  how  high  the  hills 
are  and  how  deep  the  valleys  are. 

This  is  done  by  means  of  CONTOURS,  which  are 
lines  cut  from  the  earth's  surface  by  imaginary  horizontal 
planes  at  equal  intervals  from  each  other. 

Suppose  that  the  territory  represented  by  map,  Fig.  8, 
were  submerged,  and  later  the  water  begins  to  subside 
by  a  succession  of  falls  of  the  water  level  of  20  feet,  each 
time  leaving  a  deposit  of  silt  at  the  water  line.  Even- 
tually the  whole  terrain  emerges,  and  would  appear 
roughly  as  shown  in  Fig.  9.  The  silt  deposits  of  the 
various  water  lines  would  represent  actual  contours  on 
the  terrain  itself. 

The  whole  subject  of  contours  may  be  made  absolutely 
clear  by  the  construction  of  relief  maps.  The  method 
which  will  be  described  is  a  decided  departure  from 
previous  methods.  Instead  of  the  sand  box,  moulder's 
wax  is  used.  This  material  lends  itself  admirably  to  this 
class  of  work,  due  to  the  fact  that  it  is  very  plastic, 
retains  its  consistency,  and,  when  the  relief  is  completed, 
permits  of  vivid  representation  of  all  terrain  features  by 
means  of  indentations  in  the  wax. 

In  order  to  be  successful  in  this  work  the  moulder's 
wax  must  be  used.  Do  not  attempt  to  use  the  sand 
table.  The  latter  answers  the  purpose  very  well  for 
indoor  work  in  field  fortifications,  but  it  will  not  do  for 
topographical  work.  Every  organization  and  military 
institution  should  secure  enough  of  the  wax  for  relief 

36 


RELIEF  MAPS  37 

map   construction  in   connection   with   map   reading   and 
instruction  in  Minor  Tactics. 

CONSTRUCTION  OF  RELIEF  MAPS 

The  first  necessity  is  a  table  constructed  as  shown  in 
Fig.  7.  The  two  enclosures  on  top  of  the  table  are  18" 
square,  interior  measurements  (the  same  dimensions  as 
the  Gettysburg-Antietam  12"  sheets).  The  flange  en- 
closing the  squares  is  one-fifth  of  an  inch  thick  and  an 
inch  and  a  half  in  width.  The  top  of  the  table  should 
be  perfectly  level,  and  the  flange  of  uniform  thickness 
and  planed.  Also  secure  a  rolling  pin  of  hard  wood, 


FIG.  7 

22"  long  and  about  4"  in  diameter.  A  sufficient 
amount  of  moulder's  wax  should  be  secured.  This  may 
be  purchased  from  Stewart  &  Company,  24  Broadway, 
New  York  City,  and  presumedly  from  other  dealers.  The 
wax  comes  in  different  colors;  the  olive-green  is  preferable 
for  this  work.  The  price  of  the  wax  in  small  orders  is 
about  twenty  cents  per  pound,  and,  when  ordered  in  large 
quantities,  it  may  be  secured  at  a  reduced  rate.  It  takes 
about  twenty  pounds  to  construct  one  of  the  Gettysburg- 
Antietam  12"  sheets,  but  is  well  worth  the  investment. 

As,  without  doubt,  you  will  have  need  to  use  the 
Gettysburg-Antietam  12"  sheets  in  connection  with 
studies  of  minor  tactics,  such  as  "Studies  in  Minor 
Tactics,  1915,"  and  "Small  Problems,"  etc.,  let  us 
construct  a  relief  map  of  one  of  those  sheets.  The 
necessary  12"  sheets,  unmounted,  included  in  the  texts 


38 


MILITARY  SKETCHING 


referred  to  above  may  be  secured  from  the  Book  Depart- 
ment, Army  Service  Schools,  Fort  Leavenworth,  at  a 
surprisingly  cheap  price. 

The  table,  moulder's  wax,  and  maps  having  been  se- 
cured, the  actual  method  of  construction  is  as  follows: 


FIG.  8J 

Place  a  sufficient  amount  of  wax  in  each  of  the  squares, 
and  roll  off  flush  with  the  top  of  the  squares,  so  that  you 
now  have  two  sheets  of  wax  each  one-fifth  of  an  inch 
thick.  If  the  wax  sticks  to  the  tray  and  roller,  apply  a 
little  talcum  powder  Place  the  map  over  one  of  the 


RELIEF  MAPS 


39 


squares,  and,  with  a  blunt  stylus,  trace  over  the  lowest 
heavy  contour  (20  feet)  on  the  map,  leaving  an  impres- 
sion of  same  on  the  wax.  Cut  out  that  portion  of 
the  wax  the  surface  of  which,  according  to  the  map, 


FIG.  9 


would  be  below  the  contour  just  traced.  Take  the 
remainder  of  the  sheet  of  wax  and  place  it  upon  the  base 
established  in  the  other  square.  Refill  the  square  from 
which  the  wax  has  just  been  removed,  roll  as  before, 


40 


MILITARY  SKETCHING 


and  trace  the  next  heavy  contour.  Continue  this  opera- 
tion, which  will  result  in  an  incomplete  relief  map  similar 
to  that  shown  in  Fig.  9. 


FIG.  10 

Next,  slope  off  abrupt  surfaces  between  the  heavy  contours 
by  moulding  in  small  pieces  of  wax  by  hand,  and  the  map  is 
then  completed  in  so  far  as  the  relief  is  concerned. 

Next,  all  of  the  natural  and  artificial  features  of  the  terrain 
are  represented  by  indentations  in  the  wax.  This  is  easily  done 


RELIEF  MAPS  41 

by  whittling  out  small,  soft  pine  sticks  to  represent  the  vari- 
ous conventional  signs,  as,  for  example,  a  square  end  stick  for 
buildings,  a  round  end  for  trees,  etc.  Roads  and  railroads 
may  be  draw  in  by  means  of  a  stylus  and  a  straight-edge.  Let- 
ters and  figures  may  be  drawn  in,  or,  better,  stamped  in  with 
rubber  stamps  or  steel  type.  Every  feature  is  easily  repre- 
sented, and  quickly  indented  on  the  surface  of  the  wax.  When 
you  have  no  further  use  for  a  particular  relief  map,  it  may  be 
torn  up  and  another  one  constructed  from  the  same  material. 
Fig.  10  represents  the  completed  relief  map. 

With  the  mechanical  means  explained  above,  the  student  is 
absolutely  sure  of  constructing  the  relief  map  correctly.  Hav- 
ing done  this  work,  it  follows  automatically  that  he  is  able  to 
read  a  military  map. 

The  following  principles  of  contouring  may  be  noted  in  con- 
nection with  Fig.  9 : 

1.  That  all  points  on  a  contour  line  have  the  same  elevation 
above  the  datum  plane. 

2.  That,  where  the  contours  are  equally  spaced,  the -slope  is 
uniform. 

3.  That,  where  contours  are  straight  and  evenly  spaced,  the 
ground  is  a  sloping  plane. 

4.  That  the  contours  of  a  vertical  surface  lie  on  top  of  one 
another  as  in  palisades. 

5.  That,  if  the  slope  in  rocky  formations  is  over  the  base,  then 
only  can  contours  cross. 

6.  That  every  contour  closes  upon  itself  or  extends  entirely 
across  the  map. 

7.  That  on  water-sheds  the  contours  are  con  vexed  toward 
the  base  of  the  slopes. 

8.  That  in  water  courses  the  contours  are  convex  toward 
the  sources  of  the  stream. 

9.  That  contours  far  apart  indicate  gentle  slopes. 

10.  That  contours  near  together  indicate  steep  slopes. 

SUGGESTIONS  TO  INSTRUCTORS 

As  a  knowledge  of  map  reading  goes  hand  in  hand  with 
the  study  of  tactics,  it  is  believed  that  a  few  words  at  this 


4-2  MILITARY  SKEICHIXG 

point  regarding  the  co-ordination  of  the  work  would  not  be 

It  has  been  found  by  the  author  that  pleasing  results  with 
beginners  may  be  obtained  by  constructing  relief  maps  of  the 
terrain  involved  in  small  tactical  problems.  Attention  is 
invited  to  Sketch  No.  1.  page  5,  "Studies  in  Minor  Tactics, 
1915."  Select  the  13"  sheets  comprised  in  this  section; 
build  up  each  sheet  as  above  described;  join  the  sheets  together 
and  you  have  the  desired  area  for  the  first  part  of  the  prob- 
lem. Then,  with  the  war  game  set,  you  are  ready  to  proceed 
with  the  text.  Detail  two  or  three  students  each  day  to  con- 
struct the  area  for  the  following  day.  The  relief  map  work, 
after  the  class  has  been  properly  instructed,  should  be  con- 
ducted by  detail  outside  of  the  class,  and  eventually  all  will 
have  an  opportunity  to  construct  a  relief  map  without  seri- 
ously interfering  with  their  work  or  recitations.  Having 
aD  of  the  paraphernalia  necessary  for  the  work  at  hand,  two 
men  should  be  able  to  construct  a  relief  map  of  one  of  the  13" 
sheets  in  about  two  hours. 

Assuming  that  Part  I  of  the  text  referred  to  will  constitute 
part  of  the  course:  it  deals  with  an  infantry  regiment  that 
detrains,  advances,  reconnoiters,  and  attacks  an  enemy  in 
position,  pursues,  halts  for  the  night?  establishes  outposts,  pre- 
pares and  occupies  a  defensive  position,  withdraws  therefrom 
and  retreats.  All  of  these  dispositions  are  clearly  and  vividly 
brought  before  the  mind  of  the  beginner  by  the  aid  of  the  relief 
map,  and  gains  his  interest  at  the  start.  Later,  when  all  have 
more  proficient  in  map  reading  and  tactical  disposi- 
the  ordinary  map  may  be  substituted. 

This  is  considered  an  important  lesson,  and,  to  obtain  suc- 
cessful results,  much  depends  upon  the  demonstrations  and 
explanations  of  the  instructor. 


LESSON  vm 

METHODS    OF    DETERMINING    DIFFERENCES    OF 

ELEVATION 

From  the  relief  map  constructed  in  the  previous  lesson,  the 
student  should  now  understand  what  contour  lines  are,  and 
the  necessity  of  placing  contour  lines  on  maps  in  order  to 
form  a  correct  idea  of  the  locations  and  extent  of  derations 
and  depressions  of  the  earth's  surface. 

The  surface  of  the  ground  is  either  level  or  doping.  As 
one  walks  along  a  level  course,  his  elevation  naturally  remains 
the  same,  while,  if  he  walks  along  a  sloping  course,  his  elevation 
increases  or  decreases  according  as  he  is  go  :  ; 

hill. 

It  has  been  found  that  the  up-hill  end  of  a  line  57.3  feet  long 
which  has  a  slope  of  one  degree  is  one  foot  higher  than  the 
down-hill  end.  Computing  from  these  figures,  we  are  able 
to  determine  the  difference  of  elevation  between  any  two  points 
if  we  know  the  distance  and  the  angle  of  slope  between  them. 
The  angle  of  slope  may  be  determined  by  various  instruments 
especially  prepared  for  that  purpose.  A  very  practicable 
method  of  ascertaining  angles  of  slope  is  by  means  of  the 
slope-board,  which  is  inexpensive,  easy  of  construction,  and 
never  gets  out  of  adjustment. 

CONSTRUCTION  OF  SLOPE-BOARD 

On  your  drawing  board  (see  Fig.  11),  construct  DC  per- 
pendicular to  AB,  then  when  a  point  is  sighted  along  the 
straight-edge  AB,  the  plumb  line  attached  at  D  makes  the 
same  angle  with  the  perpendicular  DC  that  AB  makes  with 
the  horizontal.  This,  of  course,  assumes  that  your  drawing 
board  is  perfectly  square. 

Lay  off  DE  5.73  inches  long  on  DC,  then,  with  the  radius 
DE  describe  the  semicircle  PEG.  Lay  off  from  E  toward  F 
and  G  successive  distances  of  one-tenth  inch  along  the  arc. 
These  divisions  represent  degrees,  because  one  degree  in  a 
circle  of  5.73  inches  radius  gives  a  chord  of  one-tenth  inch. 

m 


44  MILITARY  SKETCHING 

Extend  these  degree  marks  to  the  foot  of  the  board  with  a 
ruler  as  shown  in  Fig.  11. 

To  read  slopes,  attach  a  plumb  line  at  D,  sight  along  AB 
at  the  object,  keeping  the  board  in  a  vertical  plane.  When  the 
plumb  line  comes  to  rest,  press  the  string  against  the  edge  of 
the  board  with  the  fingers  and  read  the  angle  marked. 

OTHER  LEVELING  INSTRUMENTS 

There  are  several  varieties  of  clinometers  (hand  instruments 
for  reading  angles  of  elevation).  These  instruments,  although 
more  convenient  than  the  slope-board,  are  rather  expensive 
to  issue  to  a  large  class,  or  for  individuals  to  purchase.  If 
purchased,  full  directions  accompany  them. 

SCALES  OF  MAP  DISTANCES  AND  THEIR  USE 

Before  taking  up  the  subject  of  scales  of  map  distances,  a 
few  terms  which  will  be  used  frequently  in  the  future  will 
bear  explanation  at  this  point. 

V.  I.  means  the  vertical  interval  between  contours. 

H.  E.  (Horizontal  Equivalent)  means  the  horizontal  distance 
on  the  ground  between  two  contours. 

M.  D.  (Map  Distance)  means  the  horizontal  distance  be- 
tween two  contours  on  the  map. 

A  Normal  System  of  scales  has  been  prescribed  for  the 
U.  S.  Army  field  sketches  as  follows: 

Sketches  of  large  areas  ...   1  inch     =  1  mile,  V.  I.,  60  feet. 

Road  sketches 3  inches  =  1  mile,  V.  I.,  20  feet. 

Position  sketches 6  inches  =  1  mile,  V.  I.,  10  feet. 

Fortification  sketches 12  inches  =  1  mile,  V.  I.,    5  feet. 

It  will  be  seen  that  as  the  scale  is  increased  the  vertical  inter- 
val between  contours  is  proportionally  decreased,  so  that 
by  this  system  the  M.  D.  is  always  the  same  for  the  same 
angle  of  slope  whatever  the  scale  of  the  map  may  be. 

The  M.  D.  for  any  angle  of  slope  may  be  computed  from  the 
following  equation: 

688XR.F.  XV.L_M  D 

Angle  of  slope. 

In  which  688  equals  the  horizontal  distance  in  inches  on  a 
one-degree  slope  necessary  to  give  a  rise  of  one  foot. 


DETERMINING  DIFFERENCES  OF  ELEVATION 


45 


The  V.  I.  is  expressed  in  terms  of  feet.  However,  its  func- 
tion in  the  equation  is  only  a  relative  one  without  regard  to 
denomination. 


© 


20        15         10        5 
///////////MMllll 


)         5         .0        ,5 
llllllll\\\\\\\ 


FIG.  11 

If  the  R.  F.  and  V.  I.  for  any  sketch  made  in  accordance  with 
the  Normal  System  be  substituted  in  the  above  equation,  the 
M.  D.  will  be  the  same  for  any  particular  angle. 

In  view  of  this  let  us  substitute: 

1 

'      '  =  63360* 
V.I.  =  60. 

Angle  of  slope  =  1  degree. 

and  we  have  the  following: 

^XesleoX60 


1 

(the  M.  D.  for  one  degree  slope  for  any  sketch  under  the  Normal 
System) . 


46 


MILITARY  SKETCHING 


-I  -I  o 

Dividing  .65  by  ->  -»  -»  1,  2,  3,  4,  etc.,  we  have  the  M.  D.  for 

1      vl       3 

— »   -»    ->  1,  2,  3.  4,  etc.,  degrees  from  which  data  a  scale  may  be 
easily  constructed.     (See  Fig.  12.) 

s 


0,    0,0 


FIG.  12 

As  we  have  reading  and  working  scales  of  distances,  the  same 
applies  with  elevations.  Fig.  12  is  a  reading  scale  of  M.  D.'s 
(Map  Distances).  By  applying  this  scale  to  any  contoured 
map  under  the  Normal  System,  we  can  readily  determine  the 
degree  of  slope  between  contours,  and,  by  means  of  the  table 
below,  decide  upon  the  practicability  of  military  operations  for 
the  various  degrees  of  slope.  Students  should  be  given  an 
opportunity  to  study  contoured  maps  in  connection  with  the 
reading  scale  of  M.  D.'s  and  the  table  given  below.  The  scale 
shown  in  Fig.  12  may  also  be  used  as  a  working  scale,  but  a 
more  convenient  working  scale  will  be  explained  later  in  the 
lesson. 


Degrees 
of  slope. 


Operations. 


14  to  15 
18M 

26 


Maximum  for  railroads. 

Maximum  for  first-class  roads.  , 

Practicable  for  all  arms.     Somewhat  difficult  for  cavalry 

to  charge  descending. 
Maximum  for  cavalry  to  charge  in   mass   ascending. 

Infantry  in  close  order  descends  with  some  difficulty. 
Cavalry  can  descend  at  a  trot. 
Not  practicable  for  heavily  loaded  vehicles. 
Field  artillery  can  no  longer  maneuver. 
Maximum  up  to  which  all  arms  can  move. 
Light  vehicles  can  ascend. 
Foot  troops  can  ascend  or  descend  aided  by  hands. 


WORKING  SCALE  OF  ELEVATIONS 
We  have  learned  that  a  horizontal  distance  of 
57.3  feet  for  1  degree  slope  gives  a  rise  of  1  foot. 


or 


5730  feet  =  100  feet  rise. 

5730  feet  =  60760  inches  =  100  feet  rise. 


DETERMINING  DIFFERENCES  OF  ELEVATION  47 

Suppose  that  we  are  using  a  scale  3"  =  1  mile,  then 

1  inch  on  the  map  equals  21120  inches  on  the  ground. 
68760-=-21120  =  3M  inches  on  the  map. 


Lay  off  a  line  3)4  inches  long  and  divide  it  into  ten  equal 
parts  of  10  feet  each,  and  subdivide  each  of  the  ten  feet  divi- 
sions into  five  equal  parts  of  2  feet  each.  Place  this  scale  on 
the  same  ruler  as  your  working  scale  of  paces  or  strides,  the 
left  of  this  scale  immediately  below  the  left  of  your  working 
scale  of  paces  or  strides.  (See  Fig.  13.) 


uriiMmnnmmmiMMUiumimnmnimun 


8  ID  »  12  1%  16  16  30  It 

3irx.    =     Ixai.  33™.  PACES 

'iO  5O  6O  TO  8O  9O  1OO  Fi 


FIG.  13 

Now  suppose  that  you  have  paced  a  course  500  paces  long 
with  a  3-degree  slope.  Lay  off  your  distance  of  500  paces  from 
your  working  scale  of  paces  (the  upper  scale),  then  glance  at 
your  working  scale  of  elevations  immediately  below  the  500- 
point  on  the  upper  scale,  and  you  have  the  elevation  for  a  one- 
degree  slope;  multiply  this  result  by  three,  and  you  have  the 
difference  in  elevation  between  the  two  points  considered.  In 
a  similar  manner  a  reading  scale  of  elevations  may  be  con- 
structed under  your  6-inch  scale  of  paces  or  strides.  This 
will  cover  two  faces  of  your  triangular  working  scale.  On  the 
third  face  should  be  inscribed  a  scale  of  yards  for  3  and  6 
inches  to  the  mile  to  be  used  when  the  distances  are  estimated, 
as  may  frequently  be  the  case  in  hasty  sketching. 

The  scale  shown  in  Fig.  13  has  been  found  to  be  much  more 
practicable  at  the  Army  Service  Schools  as  a  working  scale 
than  the  one  shown  in  Fig.  12. 

Slopes  may  be  expressed  in  three  ways: 

1.  In  Degrees: 

A  one  degree  slope  indicates  that  the  angle  between  the 
horizontal  and  the  given  line  is  1  degree. 

2.  In  Percentages: 

A  slope  is  said  to  be  1,  2,  3,  etc.,  per  cent  when  100  horizontal 
units  correspond  to  a  rise  of  1,  2,  3,  etc.,  of  the  same  vertical 
units. 


48  MILITARY  SKETCHING 

3.  In  Gradients: 

Expressed  as  a  fraction  in  which  the  numerator  represents  the 
difference  in  elevation,  and  the  denominator  the  horizontal 
distance  between  the  two  points. 

Degrees  of  slopes  are  used  mostly  in  military  matters, 
percentages  for  highway  and  railway  construction  purposes, 
and  gradients  for  trench  construction.  Approximately,  1 

degree  slope  =  1.7  per  cent  slope  =  ^  gradient. 

,  QUESTIONS  FOR  REVIEW 

1.  Explain  how  to  construct  an  attachment  to  your  drawing 
board  for  reading  angles  of  slopes. 

2.  Explain    vertical   interval,    horizontal   equivalent,    map 
distance. 

3.  What  is  the  Normal  System  of  scales  for  use  in  the  U.  S. 
Army? 

4.  By  making  proper  substitutions,  determine  the  map  dis- 
tance for  J4,  1/2,  %,  1  up  to  10  degrees  of  slope,  and  construct  a 
scale  of  M.  D's.  for  same. 

5.  A  contoured  map  is  given  to  you.     From  this  map  deter- 
mine the  various  degrees  of  slope,  and  decide  upon  the  prac- 
ticability of  these  slopes  for  military  operations. 

6.  Construct  a  working  scale  of  elevations  for  3"  =  1  mile  and 
6"  =  1  mile,  each  to  read  to  an  elevation  of  100  feet.     Inscribe 
these  scales  on  your  triangular  rule  as  explained  in  this  lesson. 
(See  Fig.  13.) 

7.  In  what  three  ways  may  slopes  be  expressed?     Illustrate. 

8.  Express  a  5-degree  slope  (a)  in  percentage;  (6)  in  gradient. 


LESSON   IX 

EXERCISES  IN  CONTOURING 

We  should  now  have  a  very  good  idea  of  what  contours  are 
and  how  to  determine  the  elevations  of  locations  by  means 
of  our  scale  of  elevations. 

Before  taking  up  the  subject  of  sketching,  much  may  be 
learned  about  contouring  the  ground  to  be  sketched  by  working 
out  the  exercises  suggested  in  this  lesson.  In  actual  sketching, 
the  contour  lines  are  entirely  drawn  in  by  eye,  first  having 
given  or  assumed  the  elevation  of  a  certain  location  of  the 
ground  to  be  sketched  as  a  datum  plane,  and  also  having 
outlined  the  drainage  by  means  of  stream  lines  and  elevations 
of  certain  controlling  points.  These  controlling  points  are 
commonly  called  CRITICAL  POINTS.  Critical  points,  as 
applied  to  contours,  are  points  indicating  an  abrupt  change 
of  elevation,  as  the  top  of  a  hill,  or  an  abrupt  change  in  the 
slope  of  the  hill,  also  the  head  and  foot  of  a  ravine  or  water 
course,  the  junction  of  stream  lines,  etc.  Having  previously 
located  on  your  sketch  the  stream  lines  and  critical  points— 
in  other  words,  thoroughly  outlined  the  drainage  of  the  area — 
you  should  proceed  to  as  many  of  these  critical  points  as  will 
be  necessary  to  obtain  a  view  of  the  entire  area;  usually  two 
or  three  will  prove  sufficient,  and  you  will  find  that  from  these 
points  all  of  the  contour  lines  may  be  drawn  in  by  eye  with  a 
surprising  degree  of  accuracy. 

Figure  14  illustrates  the  idea.  Without  even  seeing  the 
area,  one  is  able,  by  means  of  the  stream  lines,  dry  water 
courses,  and  elevations  given,  to  draw  in  the  contours  about 
as  they  would  appear  if  this  sketch  were  actually  completed 
on  the  ground.  In  drawing  in  the  contour  lines,  the  student 
should  bear  in  mind  the  principles  of  contouring  given  in  Lesson 
VII.  Each  student  should  draw  in  the  contours  on  this 
sketch  with  a  soft  pencil  and  then  compare  the  results.  This 
exercise  will  impress  upon  the  mind  the  importance  in  sketching 
of  first  carefully  outlining  the  drainage  of  the  area  to  be 
sketched. 

49 


50  MILITARY  SKETCHING 

Students  should  be  given  tracing  paper  and  contoured  maps 
with  instructions  to  trace  upon  the  paper  the  stream  lines  and 
elevations  of  critical  points,  then  remove  the  tracing  paper 
from  the  map,  and  interpolate  the  contours,  afterwards  com- 
paring the  contours  interpolated  with  those  of  the  original 
map. 

One  may  obtain  a  great  variety  of  these  control  sketches 
from  the  Book  Department,  Army  Service  Schools.  Order  a 
complete  set  of  them  which  will  cost  but  a  few  cents,  and  then 
make  mimeograph  copies  for  use  of  the  class. 

It  will  be  found  that,  by  the  methods  suggested  above,  the 
student  will  soon  obtain  a  very  accurate  idea  of  what  points 
are  really  critical  in  correctly  contouring  an  area,  and,  when 
he  begins  to  sketch,  these  points  will  stand  out  vividly  on  the 
terrain  before  him. 

PROBLEM 

The  point  A,  on  a  3-inch  map,  has  an  elevation  of  780 
feet.  Given  the  azimuth  and  a  distance  from  A,  and  the 
elevation  of  the  following  points : 


Azimuth,       Distance  from  A, 

Elevation, 

Point 

degrees 

yards 

feet 

B 

20 

1,000 

920 

C 

35 

500 

865 

D 

50 

800 

820 

E 

70 

300 

820 

F 

75 

1,200 

920 

G 

90 

800 

840 

E 

110 

500 

785 

I 

115 

1,000 

890 

J 

125 

700 

780 

K 

150 

400 

745 

L 

160 

1,100 

700 

M 

180 

600 

780 

N 

200 

900 

845 

0 

220 

400 

800 

P 

245 

1,000 

895 

Q 

270 

900 

860 

R 

290 

400 

None  given. 

S 

320 

800 

880 

T 

340 

300 

810 

U 

355 

900 

840 

EXERCISES  IN  CONTOURING 


51 


87O 


860 


8/O 


797 


1=1  I  ace    /O'  Contours  on  the  above  sketch 
The  figures  jive  elevations  in  fee+ 


FIG.  14 


52  MILITARY  SKETCHING 

A  stream  flows  in  the  general  direction  U-A-K-L.  A  branch 
of  this  stream  flows  in  the  general  direction  D-K,  passing  mid- 
way between  E  and  H.  Another  branch  in  the  direction  R-A 
flowing  for  some  distance  in  the  same  general  direction.  The 
latter  branch  has  a  uniform  slope  of  one  degree. 

From  the  notes  given  above,  plot  the  stream  lines  and  critical 
points  given  and  interpolate  the  contours  so  as  to  make  a  pos- 
sible representation  of  the  relief  under  the  conditions  given. 
Remember  that  a  3-inch  map  under  the  normal  system  has  -a 
V.  I.  of  20  feet. 

NOTE. — All  information  necessary  in  the  solution  of  this  problem 
has  been  given  in  this  lesson  and  in  the  lessons  preceding  it. 


LESSON   X 
VISIBILITY 

It  is  often  necessary  in  military  operations  to  determine  from 
the  map  whether  one  point  is  visible  from  another;  whether  a 
certain  line  of  march  is  concealed  from  the  enemy;  how  much 
of  a  certain  area  can  be  seen  from  a  given  point;  and  whether 
slopes  are  uniform,  concave,  or  convex.  If  the  map  is  cor- 
rect, the  above  information  may  be  determined  very  accurately, 
but  it  must  be  remembered  that  most  maps  have  more  or  less 
minor  errors  in  relief  so  that  the  visibility  of  points,  lines,  and 
areas  cannot  be  determined  to  the  degree  of  accuracy  that  many 
may  assume;  also  the  natural  and  artificial  objects  upon  the 
earth's  surface  interfere  in  many  cases,  so  when  there  is  a 
reasonable  doubt,  and  if  the  opportunity  permits,  the  better 
method  would  be  to  actually  verify  the  visibility  by  visiting 
the  points  concerned. 

VISIBILITY  BY  INSPECTION 

1  By  studying  the  relief  map,  Fig.  9,  the  following  principles  of 
visibility  are  obvious : 

(a)  Contours  closely  spaced  on  the  top  of  a  hill,  and  grad- 
ually getting  farther  apart  toward  the  bottom,  show  a  con- 
cave slope,  and  all  points  of  the  intervening  surface  are  visible 
from  both  the  top  and  bottom  of  the  slope. 

(6)  Contours  spaced  far  apart  at  the  top  and  gradually  closer 
toward  the  bottom  show  a  convex  slope,  and  neither  end  of  the 
slope  is  visible  from  the  other. 

(c)  Contours  equally  spaced  indicate  a  plane  surface,  and  all 
intervening  points  are  visible  from  top  to  bottom  of  the 
slope. 

Bearing  the  above  principles  in  mind,  one  is  often  able  to  tell 
at  a.  glance  whether  or  not  one  point  may  be  seen  from  another. 

VISIBILITY  BY  PROPORTION 

The  line  of  sight  is  determined  by  drawing  a  line  from  the 
observing  point  tangent  to  the  point  of  probable  obstruction. 

53 


54  MILITARY  SKETCHING 

The  visibility  of  any  point,  whether  determined  by  proportion 
or  graphically,  depends  upon  the  following  simple  proportion : 


Difference   in 
elevation  of 
observing 
point     and 
point    of 
obstruction. 

Difference    in 
elevation  of 
observing 
point     and 
elevation 
necessary 
for  point  in 
question  to 
be  seen. 

Horizontal 
distance  be- 
tween    ob- 
serving 
point     and 
point    of 
obstruction. 

Horizontal 
distance  be- 
tween    ob- 
serving 
point     and 
point    in 
question. 

The  second  term  of  the  above  proportion  is  the  unknown 
quantity,  and  will  be  represented  by  "X." 

Example 

An  observing  point  has  an  elevation  of  600  feet,  the  point  of 
probable  obstruction  an  elevation  of  400  feet.  These  points 
are  800  yards  apart.  800  yards  in  prolongation  of  this  line 
is  a  hill  300  feet  high.  Can  this  hill  be  seen  from  the  observing 
point? 

Following  out  the  proportion  given  above  we  have: 

200' :Z'  -.SOp':  1600' 
or 

X=  400  feet. 

600  —  400  =  200  feet,  the  necessary  elevation  of  the  point  in 
question  in  order  to  be  visible  from  the  observing  point,  con- 
sequently the  point  may  be  seen. 

So  it  is  clear  that  in  many  cases  the  visibility  of  a  point  may 
be  determined  by  a  mental  calculation  of  the  horizontal  dis- 
tances and  the  difference  in  elevation  between  the  observing 
point,  and  the  point  of  obstruction.  The  student  should 
assume  points  and  distances  and  construct  a  diagram  illus- 
trating the  above  proportion.  By  a  few  exercises  of  this 
nature  from  a  contoured  map,  the  student  should  be  able, 
from  inspection,  to  solve  the  more  simple  problems  in  visibility. 

PROFILE  METHOD 

The  more  complicated  problems  in  visibility  may  be  readily 
solved  by  the  profile  method.  A  profile  is  a  line  supposed  to 
be  cut  from  the  earth's  surface  by  an  imaginary  vertical  plane. 
To  construct  the  profile,  project  this  line  to  scale  upon  a  vertical 


VISIBILITY  55 

plane.  (See  Fig.  17.)  You  wish  to  construct  a  profile  of  the 
line  ABC.  Place  the  lower  edge  of  a  piece  of  cross-section 
paper  along  the  line  ABC.  Pick  out  the  lowest  contour 
lines  along  ABC.  Naturally  they  are  along  the  two  streams, 
and  both  have  an  elevation  of  500  feet.  Mark  dots  on  the 
lower  edge  of  the  paper  indicating  these  lowest  contours. 
Guided  by  the  parallel  and  perpendicular  lines  of  the  cross - 
section  paper,  dot  in  the  elevations  of  the  remaining  contours, 
allowing  one  horizontal  space  for  each  contour  interval. 
Connect  these  dots  by  smooth  curved  lines,  and  you  have  the 
irregular  line  shown  in  Fig.  17.  This  is  the  profile  of  the  line 
ABC.  Then,  by  drawing  lines  of  sight  from  the  observing 
point  tangent  to  the  points  of  obstruction,  the  visible  portions 
of  the  line  ABC  are  determined. 

Visibility  problems  may  be  divided  into  three  classes: 

1.  To   determine  whether  or  not  one  point  is  visible  from 
another. 

2.  To  determine  how  much  of  the  ground  line  connecting 
the  two  points  is  visible  from  either  point. 

3.  To    determine    how  much    of    a    certain  area  is  visible 
from  a  given  point. 

VISIBILITY  OF  A  POINT 

See  Fig.  15.  Let  A  be  the  observing  point,  B  the  point  of 
probable  obstruction.  To  determine  whether  the  point  C  is 
visible  from  A.  (Note  that  the  contour  interval  is  20'.)  As 
shown  in  Fig.  16,  place  the  lower  edge  of  the  cross-section  paper 
on  the  line  ABC.  Observing  the  points,  A,  B,  and  C,  we  find 
that  A  is  the  lowest  point,  B  is  40  feet  higher,  and  C  is  il5 
feet  higher  than  A.  Let  the  space  between  the  parallel  lines 
on  the  cross-section  paper  represent  one  contour  interval,  so 
B  will  be  two  spaces  higher  than  A,  and  C  will  be  5%  spaces 
higher  than  A.  As  A  is  the  lowest  of  the  three  points,  its 
profile  position  will  be  at  the  lower  edge  of  the  cross-section 
paper,  or  is  identical  with  its  map  position.  The  profile 
position  of  B  is  6,  two  spaces  directly  over  B;  the  profile 
location  of  C  is  c,  5%  spaces  directly  over  C.  Draw  the  line 
of  sight  from  a  tangent  to  b.  It  is  found  to  pass  beneath 
c,  consequently  C  is  visible  from  A.  The  visibility  of  any 


56  MILITARY  SKETCHING 

point  may  be  determined  in  a  similar  manner.  If  there  are 
' several  points  of  probable  obstruction,  locate  the  profile 
positions  of  each  point,  and,  from  the  point, of  observation, 
draw  tangents  to  each  profile  location  and,  if  these  lines  fall 
below  the  profile  location  of  the  point  in  question,  that  point 
is  visible. 

VISIBILITY  or  A  LINE 

Construct  the  profile  of  the  line  as  previously  explained. 
From  a,  Fig.  17,  draw  lines  tangent  to  the  points  of  obstruc- 
tion, x  and  b.  (These  are  the  lines  of  sight.)  From  the 
extremities  of  the  visible  portions  of  the  profile,  drop  per- 
pendiculars to  the  line  ABC,  and  we  find,  of  the  line  ABC, 
that  AX,  YB,  and  ZC  are  visible  portions. 

VISIBILITY  OF  AREAS 

From  the  point  of  observation,  draw  several  radiating  lines 
through  the  critical  points  of  the  area  in  question.  Find  the 
visible  portions  of  these  lines  by  method  suggested  above,  and 
connect  their  extremities,  andayou  have  approximately  the 
visible  area.  (See  Fig.  18.) 

If  the  student  is  provided  with  a  well-contoured  map,  some 
cross-section  paper,  and  a  pencil,  he  should  be  able  in  an  hour's 
time,  by  the  careful  study  of  this  lesson,  to  master  the  subject 
of  visibility. 

REVIEW 

Each  student  should  be  given  a  contoured  map,  and  required 
to  solve  the  following  problems : 

1.  To  determine  the  visibility  of  a  point  by  observation. 

2.  To  determine  the  visibility  of  a  point  by  proportion. 

3.  To  determine  the  visibility  of  a  point  by  the  profile 
method. 

4.  To  determine  the  visible  portion  of  a  straight  line  by 
the  profile  method,  the  point  of  observation  being  in  the  same 
straight  line. 

5.  To  determine  the  visible  portion  of  an  irregular  line,  such 
as  a  crooked  road,  the  point  of  observation  being  outside  the 
irregular  line, 

6.  To  determine  the  visible  portion  of  a  given  area. 


PART  II 

MILITARY  SKETCHING 

Attention  is  invited  to  the  B-H  Relief  Map  designed  by 
Capt.  A.  W.  Bjornstad.  Most  of  the  leading  educational 
institutions  which  include  military  instruction  have  installed 
these  sets.  They  are  also  extensively  used  in  organizations 
throughout  the  Regular  Army  and  National  Guard.  Figs. 
25,  26,  27,  and  28,  illustrating  the  Road  Sketch,  Position 
Sketch,  Outpost  Sketch,  and  Place  Sketch,  are  taken  directly 
from  the  B-H  Relief  Map.  By  the  use  of  this  relief  map  the 
student  is  able  to  pursue  a  course  of  indoor  instruction  in  map 
reading,  and  a  course  in  topographical  sketching  which  is  every 
bit  as  realistic  and  instructive  as  actually  sketching  the  terrain. 
The  relief  map  is  of  inestimable  value  when  one  considers 
the  factors  of  time,  suitable  terrain,  and  climatic  conditions, 
to  say  nothing  of  the  great  advantage  it  affords  in  pursuing  a 
course  in  tactics,  fortification,  etc. 

In  following  the  course  of  instruction  in  sketching  outlined  in 
this  text  in  connection  with  the  B-H  Relief  Map  and  its  special 
equipment,  the  student  is  afforded  the  same  opportunities  for 
the  actual  work  of  sketching  that  present  themselves  outdoors 
on  actual  terrain. 


LESSON  XI 
FLAT  SKETCH 

Having  completed  the  course  outlined  for  map  reading,  we 
will  now  take  up  the  subject  of  military  sketching.  In  a  way 
these  two  subjects  go  hand  in  hand,  as  one  is  taught  the  other  is 
learned.  If  one  thoroughly  understands  military  sketching,  he 
naturally  will  be  able  to  read  a  military  map,  but,  for  conveni- 
ence of  instruction,  the  subjects  have  been  divided. 

Before  taking  up  the  subject  of  sketching  each  student  should 
be  equipped  with  a  drawing  board  with  an  attachment  for 
reading  angles  of  slope,  compass,  a  working  scale  as  shown  in 
Fig.  13,  Faber's  HB  pencil  or  one  of  about  the  same  degree  of 
hardness,  an  eraser,  and  a  pocket  knife  or  pencil  sharpener.  A 
tripod  in  connection  with  the  drawing  board  is  of  assistance  to 
the  beginner,  although  not  absolutely  necessary. 

The  Engineer  drawing  board  with  attached  compass  and 
tripod,  although  excellent,  is  very  expensive,  and  would  not  be 
found  practicable  on  that  account  with  large  classes  such  as 
would  be  the  case  at  educational  institutions.  The  improvised 
drawing  board  and  tripod  shown  in  Fig.  21  are  suggested.  They 
are  easy  of  construction  and  will  be  found  entirely  practicable. 

DRAWING  BOARD 

Soft  pine  board,  13"  by  14"  by  1".  This  will  allow  a  surface 
of  4  square  miles  for  a  position  sketch,  and  still  enough 
extra  space  to  secure  the  paper  to  the  board.  The  compass  may 
be  set  into  the  middle  of  one  side  of  the  drawing  board  by 
cutting  or  boring  into  the  board.  The  author  will  not  attempt 
to  recommend  any  particular  compass.  What  is  known  as  the 
watch  compass  is  issued  to  organizations  of  the  regular  army  at 
present.  Some  good  round  case  compass  that  could  be  set 
into  a  round  hole  in  the  board  is  recommended.  In  anticipat- 
ing this  course,  the  instructor  should  write  to  some  dealer  for 
samples,  and  select  the  most  practicable  compass  as  to  cost  and 
efficiency,  and  then  endeavor  to  secure  a  discount  by  ordering 
for  the  entire  class. 

62 


FLAT  SKETCH 
THE  TRIPOD 


63 


Select  a  piece  of  "Two  by  four"  5  inches  long  (see  Fig. 
21b),  and  three  sticks  4'  by  I"  by  3/2",  the  latter  of  some  tough 
material  which  will  not  be  easily  broken.  About  %"  from  the 
end  of  these  sticks  bore  holes  "  in  diameter.  At  the  mid- 


FIG.  19 


64 


MILITARY  SKETCHING 


die  of  one  end  of  the  block  saw  out  a  slit  %  "  wide  and  extend- 
ing an  inch  and  a  half  into  the  block.  By  means  of  wire  nails 
driven  as  shown  in  Fig.  21c,  attach  the  three  legs^to  the  block, 

N 


D 


N 


W 


c 

E 


E 

B 


FIG.  20 


FLAT  SKETCH  65 

one  leg  in  the  slit  and  the  remaining  two  legs  at  the  other  end 
of  the  block.  Then  drive  a  wire  nail  into  the  center  of  the  bot- 
tom of  the  block;  the  nail  being  of  sufficient  length  so  that 
it  will  protrude  %"  out  of  the  block.  (See  Fig.  21c.) 
When  all  of  this  has  been  completed,  you  will  have  a  tripod 
something  like  Fig.  21d.  Now  bore  a  hole  %"  deep 
into  the  center  of  the  bottom  of  your  drawing  board,  the 
diameter  of  this  hole  being  just  sufficient  to  accommodate  the 
wire  nail  protruding  from  the  top  of  the  tripod.  Now  attach 
the  drawing  board  to  the  tripod  by  means  of  the  nail  and  hole 
just  described,  and  you  will  have  a  drawing  board  and  tripod 
complete,  by  means  of  which  the  drawing  board  may  be  quickly 
oriented  and  leveled;  also  the  board  may  be  easily  detached 
from  the  tripod  when  it  becomes  necessary  to  read  angles 
of  slope  from  the  attachment  on  the  board.  As  stated  hereto- 
fore, the  tripod  is  of  assistance  to  the  beginner,  although  not 
really  necessary,  but  is  usually  discarded  by  the  experienced 
sketcher  as  being  too  much  bother  in  hasty  military  sketching. 

The  student,  being  equipped  as  noted  above,  is  now  ready  to 
begin  sketching. 

Fig.  19  represents  the  road  ABCD  to  be  sketched.  On 
your  paper  draw  a  straight  line  representing  the  magnetic 
north.  Mark  one  end  of  this  line  N. 

In  sketching,  always  hold  your  drawing  board  in  such  a  posi- 
tion that  the  north  end  of  the  compass  needle  and  the  arrow  end 
of  the  magnetic  north  indicated  on  the  paper  are  pointing  in  the 
same  direction.  In  the  future  we  will  refer  to  this  operation  as 
"Orienting  the  board." 

Go  to  the  point  A  on  the  road.  (See  Fig.  20.)  Orient  the 
board.  From  any  convenient  point  a  on  the  board,  draw  a 
straight  line  in  the  direction  Ab.  Next,  pace  the  distance  from 
A  to  B,  and,  with  your  scale  of  paces,  3"  =  1  mile,  lay  off  the 
line,  a&,  representing  the  distance  AB.  In  locating  the  initial 
point  a,  one  usually  knows  the  general  direction  of  the  course 
to  be  sketched,  and  should  select  a  point  of  beginning  which  will 
afford  the  greatest  use  of  the  paper.  For  example,  if  your 
course  takes  in  an  easterly  direction,  your  point  of  beginning 
should  be  near  the  west  margin  of  the  paper. 


Fig.b 


Fig.  c. 


Fig.  d 


FIG.  21 


SKETCH  OF  COUNTRY    NORTH-WEST 

OF  GREENVILLE 
By  Sgt  James  Brown,  Co.  0.  24th  Inf. 

June  16,  1916. 
Scale  3  inches  a  I  mile 
*/*  Vt  V* 


•  mile 


FIG.  22 


(J8 


MILITARY  SKETCHING 


FIG.  23 


FLAT  SKETCH  69 

Now  orient  the  board  at  B,  draw  a  straight  line  in  the  direc- 
tion BC,  pace  BC,  and  lay  off  the  line  be. 

Orient  the  board  at  C,  draw  a  line  in  the  direction  CD,  pace 
CD,  and  lay  off  the  line  CD. 

The  instructor  should  require  each  student  to  plot  a  short 
course  having  several  changes  of  direction.  The  scale  6"  =  1 
mile  might  be  used  instead  of  the  3-inch  scale,  this  making 
more  evident  all  errors  in  distance  and  direction.  Results 
should  be  compared  and  errors  pointed  out.  An  accurate 
sketch  of  the  route  should  be  exhibited,  and  each  student's 
sketch  compared  with  it. 

The  instructor  should  then  select  some  longer  course  in  which 
the  points  of  beginning  and  ending  are  the  same,  as,  for  example, 
the  course  ABCDEFA— Fig.  22.  This  will  serve  as  an 
excellent  check  on  the  work.  The  methods  employed  will  be 
the  same  as  described  above  except  that  important  points  to 
the  right  and  left  of  the  course  should  be  located  by  intersec- 
tion, and  locations  along  the  course  should  be  verified  by 
resection. 

To  LOCATE  A  POINT  BY  INTERSECTION 

NOTE — Contouring  will  not  be  attempted  in  this  sketch, 
which  is  known  as  a  "Flat  Sketch."  Vegetation  may  be 
indicated  in  writing,  and  hill  tops  indicated  by  a  dot  or  star. 
(See  Fig.  22.) 

To  locate  a  point  by  intersection — as,  for  example,  the  hill- 
top G,  Fig.  22 — orient  the  board  at  A  (see  Fig.  23  in  con- 
nection with  Fig.  22) ;  mark  the  point  a  'on  the  board  to  cor- 
respond to  A  on  the  ground.  Sight  in  the  direction  of  B, 
and  from  a  draw  a  straight  line  in  the  direction  of  B,  then 
sight  at  the  hill  G,  then  draw  a  straight  line  in  the  direction  of 
G.  '  (Care  must  be  taken  to  keep  the  board  constantly  oriented. 
In  determining  the  line  of  sight  from  the  point  of  observation 
on  the  map  to  some  distant  point  on  the  ground,  pivot  the  ruler 
at  the  point  of  observation  and  sight  along  the  upper  edge  to- 
ward the  object.)  Pace  the  distance  AB,  orient  the  board  at 
B,  and  lay  off  the  map  distance,  ab,  corresponding  to  the 
ground  distance,  AB,  then  sight  at  the  hill,  G,  and  draw  a 


70 


MILITARY  SKETCHING 


straight  line  from  b  in  the  direction  of  G.  The  lines  drawn 
from  a  toward  G  and  from  b  toward  G  intersect  at  g, 
which  is  the  map  location  of  the  hill,  G.  In  a  similar  man- 
ner any  other  points,  as  H  and  7,  Fig.  22,  may  be  located  by 
intersection  from  any  two  favorable  points. 


VrT*^ *~~?*x,~   .^  x/     ....... 


FIG.  24 


Angles  of  less  than  30  degrees  or  greater  than  120  degrees 
at  the  point  of  intersection  should  be  avoided,  as  the  two 
intersecting  lines  are  so  nearly  parallel  that  it  is  difficult  to 
locate  the  exact  point  of  intersection. 


FLAT  SKETCH  71 

To  LOCATE  A  POINT  BY  RESECTION 

Suppose  that  at  the  point  F  of  the  course  ABCDEFA,  Fig. 
22,  you  wish  to  verify  your  location.  The  points  G  and  A 
on  the  ground  have  already  been  correctly  located  on  the 
map  at  g  and  a  (see  Fig.  24).  The  sketcher  is  at  the  point 
F,  which  he  wishes  to  locate  on  the  map.  He  orients  the  board 
with  the  compass,  pivots  the  ruler  at  g,  at  the  same  time 
sighting  the  hill  6r,  and  draws  a  line  along  the  ruler  toward 
his  body.  Similarly  pivot  the  ruler  at  a,  sighting  A,  and 
drawing  a  line  along  the  ruler  toward  his  body.  This  line 
cuts  the  Gg.  The  intersection  of  the  lines  at  /  is  the 
sketcher 's  map  location. 

As  the  sketcher  passes  over  the  course,  he  should  note  in 
writing  on  his  sketch  such  ground  features  as  bridges,  fords, 
ferries,  houses,  woods,  cultivated  fields,  villages,  high  hills, 
streams,  or  any  other  information  of  importance.  (See  Fig. 
22.)  As  stated  before,  the  sketch  shown  in  Fig.  22  is  known  as 
a  "Flat  Sketch,"  no  relief  being  shown. 

When  completed,  the  following  information  should  be 
indicated  at  some  convenient  place  on  the  sketch : 

1.  Location  of  sketch. 

2.  Name  and  organization  of  sketcher. 

3.  Date  of  sketch. 

4.  Scale  of  sketch. 

5.  The  magnetic  north,  and,  if  the  declination  of  the  needle 
is  known  at  the  particular  locality,  the  true  north  should  be 
indicated  also. 

6.  Reading  scale. 

7.  Contour  interval. 

8.  Scale  of  map  distances. 

Nos.  7  and  8  need  not  be  indicated  unless  the  sketch  is  con- 
toured. 


LESSON  XII 
ROAD  SKETCH 

We  have  learned  how  to  plot  on  the  map  ground  distances, 
directions,  elevations,  and  the  various  natural  and  artificial 
ground  features  of  military  importance. 

We  will  now  make  a  complete  road  sketch.  The  instructor 
should  designate  some  road;  a  course  of  about  two  miles  with 
several  changes  of  direction  is  sufficiently  long  for  the  beginner. 
Each  student  will  go  over  the  designated  road,  plotting 
distances,  directions,  elevations,  and  important  ground 
features. 

The  sketch  should  not  only  include  the  road  itself,  but  an 
area  extending  about  400  yards  each  side  of  the  road.  As  a 
rule,  most  of  this  area  may  be  seen  from  high  elevations  along 
the  road  bed,  but  occasionally  it  may  become  necessary  to  go 
to  an  elevated  point  outside  the  road  proper  to  secure  all  of  the 
details.  Objects  of  military  importance,  such  as  high  hills, 
towns,  etc.,  which  are  more  than  400  yards  from  the  road, 
should  be  located  by  intersection.  Whenever  hills  are  located 
by  intersection,  their  elevations  should  be  noted. 

The  most  practicable  method  of  indicating  details  on 
sketches  made  in  the  field  is  shown  in  Fig.  25.  Vegetation, 
especially,  should  be  indicated  by  words  rather  than  by  the 
proper  conventional  signs.  In  short,  the  best  field  method  is 
the  shortest  and  most  accurate  method.  In  order  that  the 
student  may  become  familiar  with  all  of  the  conventional 
signs,  which  is  very  important  when  it  comes  to  map  reading, 
the  field  sketches  may  be  retouched  at  leisure,  employing 
the  proper  conventional  signs  in  each  case.  The  beginner 
should  sketch  in  every  detail  of  military  importance  in  order 
to  train  the  eye  to  observe  details.  Later  he  may  be  called 
upon  to  submit  sketches  showing  only  such  information  as 
*  may  be  required  for  particular  expeditions. 

After  the  field  work  has  been  completed,  the  instructor 
should  collect  the  sketches,  and  note  on  each  sketch  all  of  the 
glaring  defects.  Although  only  one  lesson  for  each  of  the 

72 


ROAD  SKETCH  73 

various  classes  of  sketches  is  given  in  this  text,  yet  the  same 
old  rule  of  "practice  makes  perfect"  applies. 

It  must  be  remembered  that  there  are  no  hard  and  fast  rules 
to  be  observed  in  sketching.  There  are  a  few  general  prin- 
ciples which  must  always  be  applied,  but,  when  it  comes  to 
the  details  of  the  work,  each  road  or  area  to  be  sketched  pre- 
sents new  features,  and  the  sketcher  must  use  his  judgment 
as  to  the  shortest  and  most  accurate  methods;  but,  having 
clearly  fixed  in  his  mind  the  basic  principles  such  as  distance, 
direction,  intersection,  resection,  elevations,  and  possessing 
a  keen  eye  for  critical  points  in  connection  with  the  drainage 
of  the  ground,  all  of  which  have  been  previously  explained,  he 
should  experience  no  difficulty  in  applying  the  proper  principles 
at  the  proper  time. 

A  method  of  sketching  the  road  represented  in  Fig.  25  will  be 
given  in  detail.  There  may  be  other  methods  equally  good 
as  to  the  minor  details  of  accomplishing  the  same  results. 

You  are  directed  to  sketch  the  road  beginning  at  the  bridge 
near  the  Langford  house,  thence  about  two  miles  to  the  north, 
Fig.  25.  It  will  be  noted  that  this  road  has  frequent  changes  of 
direction,  which  will  require  more  "Set  ups"  than  in  the  case  of 
a  more  direct  route.  It  is  assumed  that  the  elevation  of  the 
floor  of  the  bridge  is  90  feet.  In  case  the  elevation  of  the  point 
of  beginning  is  not  known,  it  always  may  be  assumed,  and  your 
elevations  will  be  relatively  correct  throughout  the  sketch. 

Orient  the  board  at  1,  and  indicate  your  magnetic  meridian 
as  explained  heretofore.  Sight  in  the  direction  of  2.  (the 
first  change  of  direction  in  the  road),  and  draw  a  straight  line 
in  the  direction  of  2.  Then  proceed  to  2,  and  on  arriving  there 
you  have  determined  the  distance.  Note  down  the  location  of 
2,  and,  from  points  1  and  2,  plot  in  such  details  as  the  stream 
railroad,  buildings  at  the  Langford  house,  etc.  Continue  the 
work  along  the  same  lines  at  3,  4,  5,  6,  7,  8,  etc. 

Now  the  subject  of  contours  comes  in.  If  the  correct 
methods  are  pursued,  the  contouring  will  be  found  to  be  very 
simple  and  interesting.  Do  not  attempt  to  get  the  angles  of 
slope  to  2,  3,  4,  and  5,  as  the  change  of  elevation  is  so  slight. 
Remember  the  principles  of  contouring  brought  out  in  Lesson 


ROAD    SKETCH 
NEAR  LANGFORD  BRIDGE 

June  16,1916 
By  ls+  Lieut   FB  SMITH.ICHh  Inf 

Scale  3"  =  I  mile 


100^0  |  (  t  [         600 


M.D 


V.I.  20' 
FIG.  25 


ROAD  SKETCH  75 

IX.  Bearing  in  mind  those  principles,  what  are  the  critical 
points  which  determine  the  drainage  of  this  route?  They  are 
1,  6,  and  the  stream  crossing  north  of  8,  also  A,  B,  C,  and  D. 
How  are  those  elevations  determined?  Intersect  on  A  from  1 
and  6,  then,  knowing  the  elevation  of  1,  the  elevations  of  A  and 
6  are  determined  by  methods  previously  explained.  Inter- 
sect on  B  and  C  from  6  and  stream  crossing  north  of  8,  and  so 
on  throughout  the  sketch.  Never  attempt  to  determine  the 
slope  at  each  change  of  elevation  in  the  road.  It  is  an  endless 
task,  your  error  multiplies,  and  in  a  short  time  you  have  lost 
control  of  your  relief  entirely. 

Then,  as  explained  in  Lesson  IX,  having  determined  the 
elevations  of  the  three  stream  crossings  and  A,B,C,  and  Z),  and 
noting,  as  you  pass  along  the  road,  the  direction  of  the  stream 
lines  and  the  general  directions  of  the  spurs  leading  down  from 
the  hill  tops,  you  cannot  go  far  stray  in  interpolating  your 
contours  from  good  observing  points  along  the  road  bed  or  in 
close  proximity  thereto. 

A  FEW  RULES  TO  BE  OBSERVED 

1.  The  beginner  should  not  attempt  to  hurry,  even  if  he  is 
unable  to  complete  the  task  assigned  to  him. 

2.  Devote  equal  time  and  care  to  all  parts  of  the  sketch. 

3.  Be  sure  that  your  orientations  are  correct,  and  that  your 
board  is  kept  oriented  at  all  times. 

4.  Do  not  leave  a  station  until  all  of  the  necessary  details 
up  to  that  point  have  been  put  in. 

5.  Do  not  attempt  to  show  too  minute  details.    You  must  get 
the  distances,  directions,  elevations  of  critical  points,  and  by 
intersection  locate  such  land  marks   as  may   assist  you  in 
identifying  your  location  later,  or  that  are  of  military  impor- 
tance, such  as  high  hills,  towns,  etc.     By  close  observation 
and  taking  a  few  notes  as  you  pass  along  the  road,  the  remain- 
ing details  such  as  fences,  cultivated  fields,  buildings,  cuts  and 
fills,  bridges,  railroad  crossings,  telegraph  lines,  etc.,  may  be 
filled  in  from  good  observing  points. 

6.  Be  sure  that  the  drainage  has  been  properly  outlined  be- 
fore attempting  to  put  in  the  contour  lines,  in  other  words, 


76  MILITARY  SKETCHING 

first  locate  conspicuous  hill  tops,  the  directions  of  spurs 
leading  therefrom,  and  the  courses  of  stream  beds  and  valleys. 
This  is  most  important,  as  the  drawing  in  of  contour  lines 
without  first  indicating  what  may  be  called  the  framework  of 
the  drainage  would  be  like  fitting  a  garment  without  making 
previous  measurements. 

7.  To  become  a  rapid  and  accurate  sketcher,  one  must  be 
able  to  estimate  distances  with  a  considerable  degree  of  accu- 
racy (see  estimating  distances,  Small  Arms  Firing  Regulations, 
U.  S.  Army). 


LESSON  XIII 
POSITION  AND  OUTPOST  SKETCHES 

Military  sketches  may  be  classified  as  "Road  Sketches" 
and  "Area  Sketches."  We  have  already  discussed  the  road 
sketch  in  Lesson  XII.  Area  sketches  are  classified  as  follows: 

1  The  Position  Sketch. — This  is  a  sketch  of  any  military 
position,  such  as  a  camp  site,  or  any  position  to  be  occupied  by 
a  body  of  troops.  Conditions  are  such  that  the  sketcher  is  at 
liberty  to  visit  any  part  of  the  area  to  be  sketched. 

2.  Outpost   Sketch. — A   sketch   of   a   friendly  outpost  line. 
The  sketcher  is  usually  at  liberty  to  visit  all  portions  of  the 
area  in  rear  of  the  line  of  observation.     Details  between  the 
line  of  observation  and  the  hostile  position  are  usually  obtained 
by  intersection  and  observation. 

3.  Place  Sketch. — A  sketch  of  an  area  made  by  the  sketcher 
from  one  point  of  observation,  as  the  sketch  of  an  area  or 
a  road  from  an  advanced  point  of  an  outpost  line  toward 
the  hostile  position.  4 

In  this  lesson  we  will  consider  the  position  sketch  and  the 
outpost  sketch.  The  scale  of  these  sketches  is  6"  =  1  mile 
with  a  contour  interval  (V.  I.)  of  10  feet. 

POSITION  SKETCH 

The  work  involved  in  making  a  position  sketch  may  be 
summarized  as  follows: 

1.  Look  over  the  ground  to  be  sketched  from  some  good 
point  of  observation. 

2.  Select  and  measure  a  base  line. 

3.  Locate  by  intersection  as  many  critical  points  as  possible 
from  the  extremities  of  the  base  line. 

4.  Select  and  traverse  the  most  practicable  route  in  the 
area  such  as  roads.     If  there  are  no  roads,  then  the  route  which 
will  most  assist  you  in  the  location  of  details.     In  traversing, 
check  your  horizontal  and  vertical  locations  by  resection. 

5.  Then  go  to  some  good  points  of  observation  and  complete 
the  sketch   as   to   the   remaining   topographical   details   and 

77 


78  MILITARY  SKETCHING 

contour  lines  not  completed  in  the  traverse.     (As  to  the  inter- 
polation of  contours,  see  Lesson  IX.) 

Many  experienced  sketchers  may  have  other  methods  of 
approaching  the  work,  but  the  method  outlined  above  is  a 
practicable  one  for  the  beginner,  from  which  he  may  depart 
in  some  particulars  as  he  becomes  more  experienced.  The 
nature  of  the  terrain  to  be  sketched  is  also  a  factor  in  the 
methods  to  be  pursued. 

BASE  LINE 

The  mapping  of  areas,  either  by  hasty  sketching  methods. 
or  by  means  of  an  accurate  instrumental  survey,  depends 
primarily  upon  some  system  of  triangulation.  By  triangula- 
tion  is  meant  the  establishing  of  a  series  of  triangles  covering 
the  area  to  be  mapped,  by  means  of  which  critical  points  are 
located  horizontally  and  vertically.  As  heretofore  stated,  the 
angles  of  these  triangles  should  not  be  less  than  30  degrees  nor 
greater  than  120  degrees. 

The  base  line  should  be  located  as  near  the  center  of  the 
area  as  practicable,  and,  in  sketching  small  areas,  should  be 
about  one-third  as  long  as  the  greatest  dimension  of  the  area. 
It  should  be  on  as  level  ground  as  practicable  with  a  good  view 
over  the  ground  to  be  sketched,  and  its  ends,  if  possible,  should 
be  identified  by  some  conspicuous  natural  or  artificial  objects. 
Naturally,  it  is  not  always  possible  to  fulfill  all  of  these  condi- 
tions. In  hasty  sketching,  the  length  of  the  base  line  is 
determined  by  pacing  or  strides,  exercising  as  much  care  as 
possible,  as  it  is  obvious  that  the  accuracy  of  the  sketch  depends 
upon  the  measurement  of  the  base  line. 

The  horizontal  and  vertical  positions  of  the  vertices  of  the 
triangles  are  located  either  by  intersection  or  resection.  (See 
Fig.  26  and  Fig.  27.)  Points  1  and  2  locate  the  extremities  of 
the  base  line.  Points  3  and  4  are  located  by  resection,  and 
points  A,  B,  C,  D,  E,  F,  and  G  by  intersection. 

Method  of  orienting,  determining  distances  and  directions, 
the  location  of  points  by  intersection  and  resection  have 
been  previously  explained.  In  view  of  this,  it  will  not  be 
necessary  to  go  into  detail  in  explaining  the  method  of  opera- 


POSITION  AND  OUTPOST  SKETCHES 


79 


tions  pursued  in  obtaining  Fig.  26,  which  is  the  triangulation 
scheme  involved  in  the  position  sketch  shown  in  Fig.  27.  A 
brief  description  of  methods  pursued  in  the  position  sketch 
shown  in  Fig.  27  will  be  given,  however,  in  which  the  terms 

90 


195 

G 


4* 


3^/20 

\ 
\ 
\ 
\ 


Frame  Work 
POSITION  SKETCH 
Scale  6"  =  I  mile 


80  MILITARY  SKETCHING 

used  in  this  paragraph  will  be  used  freely  without  further 
explanation. 

METHOD  IN  DETAIL  OF  SKETCHING  POSITION  SKETCH,  FIG.  27 

Assume  that  from  some  good  observing  point  you  have 
selected  the  line,  1-2,  as  the  base  line.  You  are  given  the 
altitude  at  1,  or  the  altitude  may  be  computed  from  some 
nearby  bench  mark,  or  the  altitude  of  1  may  be  assumed. 
In  this  case  we  will  assume  that  the  altitude  at  1  is  228  feet. 

Set  up  and  orient  at  1 .  Draw  a  straight  line  in  the  direction 
of  2,  also  determine  the  angle  of  slope  from  1  to  2.  Before 
leaving,  draw  radiating  lines  to  as  many  critical  points  as  will 
assist  you  in  outlining  the  drainage  of  the  area.  The  nature 
of  these  points  has  been  explained  in  previous  lessons.  In 
selecting  the  critical  points,  select  such  points  as  will  probably 
be  seen  from  2.  Next,  pace  the  distance  to  2.  In  doing  so, 
note  the  distance  to  the  road  and  to  the  stream,  also  the 
elevation  of  each  of  these  points.  Arriving  at  2,  lay  off  the 
distance  and  note  the  elevation  of  2,  and  set  up.  At  2  complete 
the  intersection  of  points  sighted  from  1,  and  note  the  elevations 
of  these  points.  Next,  proceed  to  the  road  near  by,  and  locate 
your  map  position  either  by  resection  or  by  traversing  the 
distance,  then  traverse  the  entire  road,  following  out  methods 
suggested  under  "Road  Sketch"  in  the  previous  lesson.  Then 
by  setting  up  at  a  few  good  observation  points  such  as  1  and  2, 
and  possibly  some  others,  and  aided  by  the  traverse  and  critical 
points  located,  you  are  able  to  complete  the  sketch  from 
observation,  filling  in  the  remaining  topographical  details, 
and  interpolating  the  contours  as  suggested  in  Lesson  IX. 

One  of  the  greatest  assets  to  the  sketcher  is  an  eye  for  critical 
points.  REMEMBER  THAT  THE  CORRECT  LOCA- 
TION OF  THE  CRITICAL  POINTS  DETERMINES  THE 
DRAINAGE  OF  THE  AREA,  AND  WITH  THE  CORRECT 
DRAINAGE  ESTABLISHED,  YOU  HAVE  THE  KEY  TO 
THE  SKETCH. 

The  sketcher  soon  discovers  many  short  cuts  in  the  work. 
Every  area  to  be  sketched  is  different,  and  requires  a  brief 


too       o 
1,1,1 1 I  I 


POSITION    SKETCH 

NEAR    BENSONS   CORNERS 

June  16  1916 
By  Isi-  Lieu-h  F.B.SMITH.IOIh.lnf. 

Scale  6"=  Imile 
soo 


iOOOYOS 


M.D. 
I*  I       2e     I     3°   I  4*1  5  16  I7ISI9II 


V.I.  10' 
FIG.  27 


82  MILITARY  SKETCHING 

estimate  of  the  situation  from  some  good  observing  point  be- 
fore taking  up  the  work  in  order  to  take  the  greatest  advantage 
of  the  terrain.  However,  by  following  out  the  suggestions  of 
this  lesson,  the  beginner  will  not  go  astray,  and,  with  experience, 
the  short  cuts  will  dawn  upon  him. 

OUTPOST  SKETCH 

The  general  plan  of  making  an  outpost  sketch  is  the  same  as 
with  the  position  sketch,  with  some  few  exceptions  as  follows: 

The  base  line  must  be  along  the  line  of  observation  or  a 
sufficient  distance  in  rear  with  a  view  of  locating  as  many  points 
along  the  line  of  observation  as  possible,  these  latter  points  to 
be  used  in  locating  points  toward  the  hostile  position  either  by 
intersection  or  observation.  In  making  an  outpost  sketch,  it  is 
usually  impossible  to  visit  that  portion  of  the  area  beyond  the 
line  of  observation,  hence  all  points  beyond  this  line  must  be 
located  either  by  intersection  or  observation. 

In  addition  to  the  topographical  features  of  military  im- 
portance, the  locations  of  the  various  parts  of  the  outpost 
should  be  indicated.  In  this  connection,  the  student  should 
consult  the  Field  Service  Regulations,  1914,  paragraphs  60-83 
inclusive. 

REVIEW 

1.  Describe  the  nature  of  a  Position  Sketch;    an   Outpost 
Sketch;  a  Place  Sketch. 

2.  What  are  the  various  steps  to  be  taken  in  making  a  posi- 
tion sketch? 

3.  What  is  meant  by  the  triangulation  of  an  area? 

4.  What  is  the  base  line  and   what   conditions   should   it 
fulfill? 

5.  In  what  two  ways  are  the  vertices  of  the  various  triangles 
located? 

6.  What  are  the  degree  limits  of  angles  of  the  triangles? 

7.  What  is  the  key  to  successful  sketching? 

8.  In  what  particulars  does  an  outpost  sketch  differ  from  a 
position  sketch? 


LESSON  XIV 
PLACE  SKETCH 

It  is  often  necessary  to  sketch  a  certain  area  from  one 
point  of  observation.  This  is  called  a  "Place  Sketch."  It  is 
also  made  on  the  same  scale  and  with  the  same  V.  I.  as  the 
position  sketch. 

In  time  of  war  there  is  a  great  demand  for  sketches  of  this 
class.  Fig.  28  illustrates  the  method  of  construction  which 
is  very  simple,  providing  that  the  student  understands  the 
basic  principles  of  sketching  brought  out  heretofore.  However, 
in  order  to  produce  a  place  sketch  of  value,  the  sketcher  must 
possess  the  ability  to  estimate  distances  with  a  considerable 
degree  of  accuracy.  Telephone  and  telegraph  poles  are 
usually  set  up  at  fixed  distances  which  often  are  of  great 
assistance.  In  many  parts  of  the  country  the  land  is  divided 
into  sections,  and  the  sections  subdivided  in  such  a  manner  as 
will  aid  the  sketcher  in  making  correct  estimations. 

As  estimations  of  distances  are  made  in  yards,  a  working 
scale  of  yards,  6"  equals  one  mile,  is  necessary.  The  student 
has  already  been  instructed  to  place  a  scale  of  yards  on  his 
triangular  working  scale. 

You  are  in  charge  of  a  patrol  operating  in  hostile  territory. 
Your  patrol  is  concealed  at  some  point  north  of  A,  Fig.  28. 
You  proceed  to  the  high  point  A9  and  discover  that  a  hostile 
force  consisting  of  one  infantry  battalion  is  going  into  camp  at 
Bethel  Church.  It  is  assumed  that  you  are  in  hostile  territory, 
and  that  you  have  no  good  maps  of  this  particular  terrain,  as 
often  may  be  the  case.  In  that  event,  the  message  that  you 
are  about  to  send  will  be  of  much  greater  value  to  your  com- 
manding officer  if  accompanied  by  a  sketch. 

As  it  is  obvious  the  entire  sketch  must  be  made  from  the 
one  point  of  observation,  A,  hence  the  term,  place  sketch.  It 
is  also  obvious  that  the  entire  sketch  must  be  made  from 
observation.  Sketches  of  this  class  are  hastily  made  on  the 
back  of  the  message  forms  furnished  organizations  in  the  field. 

First  orient  your  message  book,  then  look  over  the  area  to 
be  sketched,  and  endeavor  to  locate  some  feature  or  features 

M 


84 


MILITARY  SKETCHING 


r Reverse  slope 
of  hill  which 

cannot  be  seen 

from   A 


too 

L_L 


J L 


PLACE  SKETCH 

NEAR  BETHEL  CHURCH 

June  16,1916 
By  1st  L.eu+  F.B.SMITH,lOth.lnf 

Scale  6"=  Imile 

500 
_! I  I I 


IOOOYDS 


M.D. 
I       2°    I     3-|  *f  IS  |6|7|fl|9[io| 


V.I.  10' 


PLACE  SKETCH  85 

of  the  terrain  which  will  best  serve  the  purpose  of  a  framework 
upon  which  to  connect  up  the  remaining  details  of  the  area. 
Roads,  if  available,  will  answer  the  purpose  very  well,  espe- 
cially where  there  are  telephone  poles.  The  rifle  sight  leaf 
and  the  mil  scale  will  be  found  of  value  in  estimating  dis- 
tances. In  this  case,  by  the  aid  of  the  telephone  poles,  and 
rays  drawn  to  the  various  critical  points  of  the  area,  a  fairly 
accurate  framework  may  soon  be  established  upon  which 
the  remaining  topographical  features  may  be  connected  up. 

As  to  the  contour  lines,  assume  as  the  datum  plane  the  down- 
stream end  of  the  largest  stream,  and,  for  convenience,  call 
this  elevation  zero,  or  assume  some  elevation  for  your  lowest 
contour  as  100  feet,  as  is  the  case  in  Fig.  28.  Then  compare 
your  own  elevation  with  that  of  the  datum  plane  and  other 
critical  points  which  have  been  located  by  rays  drawn  from 
A  and  estimation.  It  only  remains  then  to  interpolate  your 
contours  in  the  same  manner  as  was  explained  in  discussing 
the  position  sketch. 

Field  glasses  are  of  great  assistance  in  making  place  sketches. 

A  series  of  place  sketches  made  along  an  outpost  line  is  often 
of  great  advantage.  All  staff  officers  and  artillery  reconnais- 
sance officers  should  be  skilled  in  making  place  sketches. 

As  an  exercise,  the  following  is  suggested:  The  instructor 
will  post  each  member  of  the  class  in  the  same  locations  as  he 
might  the  outguards  of  an  outpost,  and  require  each  student  to 
make  a  place  sketch,  including  a  certain  well-defined  sector  in 
front  of  his  position.  When  the  sketches  are  completed,  the 
instructor,  accompanied  by  the  entire  class,  will  proceed  in 
turn  to  each  of  the  positions  occupied  by  the  sketchers. 
Members  of  the  class,  other  than  the  sketcher  who  occupied  the 
position,  will  be  required  to  orient  the  sketch  and  check  the 
distances  and  directions,  and,  in  fact,  review  the  entire  sketch. 
By  this  method  many  points  will  be  brought  out,  and,  at  the 
same  time,  each  student  will  be  keen  to  do  his  best,  knowing 
that  his  work  is  to  be  reviewed  by  the  entire  class. 

A  keen  eye  for  critical  points,  the  correct  estimation  of 
distances,  and  speed  are  qualities  that  a  good  place  sketcher 
must  possess. 


LESSON  XV 

MISCELLANEOUS 

TOPOGRAPHICAL  RECONNAISSANCE  REPORTS 

A  topographical  reconnaissance  usually  consists  of  a  sketch 
and  a  report.  As  many  of  the  required  details  as  possible 
should  be  shown  on  the  sketch.  Additional  information,  such 
as  would  be  required,  may  be  shown  in  marginal  notes  on  the 
sketch,  or,  if  this  is  not  found  to  be  practicable,  a  separate 
report  may  be  made  and  appended  to  the  sketch. 

The  report  should  be  as  brief  as  possible  consistent  with 
rendering  all  of  the  desired  information.  Frequently  sketches 
do  not  contain  a  sufficient  number  of  reference  points  upon 
which  to  base  a  concise  report,  or  to  formulate  a  concise  field 
order.  If  such  is  the  case,  additional  reference  points,  such  as 
letters  or  numbers,  should  be  added  to  mark  road  crossings 
etc.  Conspicuous  hill  tops  and  road  crossings  are  commonly 
indicated  by  their  elevations.  These  reference  marks  should 
be  clearly  indicated,  and,  on  a  sketch  in  connection  with  a  re- 
port, they  may  be  indicated  in  red  or  some  other  bright  color 
that  will  immediately  attract  the  reader's  attention. 

The  following  pertaining  to  field  orders  is  quoted  from  the 
Field  Service  Regulations,  1914,  and  apply  equally  as  well  in 
Topographical  Reconnaissance  Reports: 

"Field  orders  must  be  clear  and  definite.  Expressions  de- 
pending upon  the  viewpoint  of  the  observer,  such  as  right,  left, 
in  front  of,  behind,  on  this  side,  beyond,  etc.,  are  avoided,  ref- 
erence being  made  to  the  points  of  the  compass  instead.  The 
terms  right  and  left,  however,  may  be  applied  to  individuals  and 
bodies  of  men,  or  to  the  banks  of  a  stream;  in  the  latter  case  the 
observer  is  supposed  to  be  facing  down  stream.  The  terms 
right  flank  and  left  flank  are  fixed  designations.  They  apply 
primarily  to  the  right  and  left  of  a  command  when  facing  an 
enemy,  and  do  not  change  when  the  command  is  retreating. 
The  head  of  a  column  is  its  leading  element,  no  matter  in  what 
direction  the  column  is  facing;  the  other  extremity  is  the  tail. 

86 


MISCELLANEOUS  87 

"To  minimize  the  possibility  of  error,  geographical  names  are 
written  or  printed  in  ROMAN  CAPITALS ;  when  spelling  does 
not  conform  to  the  pronunciation,  the  latter  is  shown  phonetically 
in  parentheses,  thus:  BICESTER  (Bister),  GILA  (Hee'la). 

"When  two  or  more  places  or  features  on  the  map  have  the 
same  name  they  are  distinguished  by  reference  to  other  points. 

"A  road  is  designated  by  connecting  two  or  more  names  of 
places  on  the  road  with  dashes,  thus:  LEAVENWORTH- 
LOWEMONT-ATCHINSON  road." 

There  are  as  many  classes  of  topographical  reports  as  there 
are  demands  for  sketches,  each  case  differing  slightly  according 
to  the  particular  information  desired,  but  always  coming  under 
a  few  general  headings  such  as  the  reconnaissance  of  a  road,  a 
railroad,  a  river,  camp  sites,  positions  to  be  occupied  by 
troops,  etc. 

ROAD  RECONNAISSANCE  REPORT 

In  addition  to  the  information  shown  on  the  road  sketch,  the 
report  might  elaborate  on  such  points  as  the  following:  steep 
grades,  width  of  roadway;  if  paved,  the  width,  class,  drainage, 
and  condition  of  paving;  if  dirt  road,  its  soil  and  general  con- 
dition. Can  foot  troops  march  along  its  side  between  the 
wagon  track  and  fences  ?  Advantageous  infantry  and  artillery 
positions  with  range,  etc. 

Bridges:  Complete  information  regarding  piers,  abutments 
and  superstructure;  width,  clear  head  room,  safe  load,  also  the 
nearest  bridge  above  or  below  with  similar  information. 

Country:  Any  additional  information  pertaining  to  the  vege- 
tation or  soil  that  cannot  be  shown  on  the  sketch. 

Streams  Crossed:  Additional  information  pertaining  to 
streams  crossed,  such  as  width,  depth,  and  surface  velocity; 
velocity  to  be  indicated  as  sluggish,  moderate,  quick,  and  swift; 
availability  of  water  for  various  camp  purposes;  fords  at  or 
near  crossing,  with  complete  description  of  same;  practicable 
for  what  class  of  shipping. 

Towns  and  Villages:  Name  and  location  on  sketch;  material 
and  size  of  buildings;  distribution  of  buildings;  population; 
location  of  depots,  telegraph  and  telephone  offices;  water  sup- 


88  MILITARY  SKETCHING 

ply;  sanitation;  important  public  buildings  and  repair  shops; 
food  supply.  In  fact  an  exhaustive  report  would  involve  too 
many  details  to  enumerate  here. 

Railroads  Crossed:  Name,  gauge,  single  or  double  track, 
sidings,  loading  facilities,  name  and  description  of  nearest 
station,  etc. 

RAILROAD  RECONNAISSANCE  REPORT 

In  friendly  territory  all  information  necessary  could  be  ob- 
tained from  the  proper  railroad  officials,  but  in  hostile  territory 
this  information  would  have  to  be  obtained  by  reconnaissance, 
and  could  be  obtained  better  by  an  officer  familiar  with  railroad 
conditions  and  the  needs  of  the  military  service.  Generally, 
the  report  would  pertain  to  such  matters  as  the  following: 

The  Line:  Name,  terminal  points,  stations  and  distances  be- 
tween same,  gauge,  single  or  double  track,  ties,  rails,  condition 
of  road  bed,  drainage,  liability  to  washouts,  material  and  facili- 
ties for  repairs,  marching  of  troops  on  right  of  way. 

Rolling  Stock:  Amount  available  for  the  particular  section 
reported  on;  location  of  repair  shops  and  their  capacity;  any 
other  details  depending  upon  the  rolling  stock. 

Stations:  Name  and  location;  entraining  and  detraining 
facilities  such  as  sidings;  ramps,  turn  tables,  water  tanks,  fuel 
supply,  storage  facilities,  derricks,  etc. 

RIVER  RECONNAISSANCE  REPORT 

General  description  of  river  valley  as  to  limiting  ranges, 
roads  paralleling  river,  passes,  infantry  and  artillery  positions 
controlling  river,  and  any  other  data  not  shown  on  the  sketch. 

The  Stream:  Its  width,  depth,  velocity,  navigability,  any 
obstruction  to  navigation,  information  pertaining  to  high  and 
low  water  marks,  character  of  banks,  quality  of  water,  and 
source  of  contamination. 

Canals:  Width,  depth,  navigability,  all  information  per- 
taining to  the  locks,  means  of  destroying  locks  and  the  effect. 

Bridges,  Fords,  and  Ferries:  For  bridges,  note  the  navigable 
width  between  piers,  height  of  superstructure  above  water  at 
the  various  water  marks;  with  drawbridges,  note  dimensions 


MISCELLANEOUS  89 

and  method  of  operation.  Note  the  exact  location  of  fords, 
length,  width,  and  nature  of  bottom,  practicability  of  troops 
crossing  (see  page  208,  F.  S.  Regs.).  Practicability  of  ferries 
for  the  various  classes  of  troops,  class  of  ferry,  power.  Data 
pertaining  to  all  classes  of  shipping  available  in  the  river. 
Suitable  defensive  positions  for  bridges,  fords,  and  ferries. 

CAMP  SITE  AND  POSITION  RECONNAISSANCE  REPORTS 

See  F.  S.  Regs.,  1914,  for  requisites  of  a  camp  site  and  of  a 
defensive  position. 

As  a  general  rule,  endeavor  to  place  yourself  in  your  com- 
manding officer's  position  and  decide  upon  everything  that 
he  would  naturally  wish  to  know  in  each  particular  case. 

MAP  REPRODUCTION 

Military  maps,  to  be  of  any  use,  must  be  reproduced  in 
sufficient  numbers  to  accommodate  all  who  need  them  in  the 
field  of  operations.  Of  course  there  are  many  road,  position, 
and  place  sketches  which  are  hastily  made  in  order  to  convey 
information  of  no  general  importance.  In  many  cases  of  this 
kind  the  original  sketch  will  answer  all  purposes  and  no  repro- 
duction is  necessary. 

Maps  may  be  reproduced  : 

1.  By  Tracing. — Attach  a  piece  of  tracing  paper  or  tracing 
cloth  over  the  map  to  be  copied,  then  trace  over  the  details 
with  ink  or  pencil, 

2.  Carbon  Paper. — Place  a  sheet  of  carbon  paper  over  the 
sheet  on  which  the  copy  is  to  be  made,  then  fasten  the  map 
on  top  of  the  carbon  sheet  and  trace. 

3.  Blue  Print. — Secure   a   sufficient   amount   of   blue-print 
paper,  a  commercial  product  which  may  be  secured  from  any 
photographer  or  local  engineer  office;  also  secure  a  suitable 
frame  which  is  merely  a  rectangular  frame  holding  a  piece  of 
glass.     The  back  of  the  frame  should  be  padded  so  as  to  fit 
close  to  the  glass.     The  process  of  printing  is  simply  to  expose 
the  tracing  to  the  sunlight  with  the  blue  print  paper  under- 
neath, sensitized  side  next  to  the  tracing.     The  length  of  time 
exposed  depends  upon  the  sensitiveness  of  the  paper  and  the 


90  MILITARY  SKETCHING 

nature  of  the  light.  The  time  may  vary  from  twenty  seconds 
to  several  minutes. 

4.  Negative. — From  the  negative  of  a  map  by  photographic 
methods. 

5. — Also  lithographic  and  photolithographic  methods. 

REPRODUCTION  WITH  CHANGE  OF  SCALE 

1.  Pantograph. — An  instrument  composed  of  several  pieces 
of  metal  or  wood  joined  in  such  a  way  as  to  form  a  parallelo- 
gram.    The  sections  of  the  instrument  are  so  arranged  that,  by 
tracing  over  the  map  with  one  of  the  bearing  points,  another 
bearing  point  will  reproduce  the  map  to  the  same  or  a  different 
scale  according  to  the  adjustment. 

2.  By  Squares. — Divide  the  original  map  into  squares  of 
suitable  dimensions.     The  size  of  the  squares  depend  some- 
what upon  the  amount  of  detail  to  be  shown.     Divide  the 
sheet  upon  which  the  copy  is  to  be  made  into  an  equal  number 
of  squares,  the  dimensions  of  these  squares  being  regulated 
by  the  scale  of  the  map  to  be  reproduced.     Draw  in  each 
square  the  details  of  the  corresponding  square  of  the  original. 
In  order  to  avoid  error,  the  squares  of  the  original  and  the 
reproduction  should  be  correspondingly  numbered. 


APPENDIX 

SUGGESTIONS    FOR    INSTRUCTION    AT    TRAINING 

CAMPS 

The  author  has  had  considerable  experience  in  instruction 
pertaining  to  this  subject  at  training  camps,  and  the  following 
suggestions  may  prove  of  some  value  to  those  upon  whom  this 
duty  may  fall  in  the  future. 

With  the  intensified  course  of  training  pursued  at  training 
camps,  the  time  usually  allotted  to  this  subject  is  very  limited, 
possibly  not  more  than  a  half  dozen  periods  of  two  hours  each, 
so  that  it  is  a  foregone  conclusion  that  the  instructor  must 
work  against  time  throughout  the  course.  Another  handicap 
is  the  limited  number  of  instructors  proportionate  to  those 
undergoing  instruction,  but,  regardless  of  these  serious  disad- 
vantages, much  may  be  accomplished  if  the  right  methods  are 
pursued. 

Let  us  first  consider  the  necessary  preparations  to  be  made 
by  the  instructor  previous  to  the  first  instruction  period. 
Aside  from  the  authorized  text-book,  the  student  will  require 
the  following  articles : 

1.  Drawing  board  with  slope  board  attachment. 

2.  Compass. 

3.  Triangular  ruler. 

4.  Pencil,  Faber's  HB. 

5.  Eraser.     . 

6.  Four  thumb  tacks. 

7.  Drawing  paper. 

DRAWING  BOARD 

With  large  classes  it  is  obvious  that  it  would  not  be  practi- 
cable to  provide  Engineer  drawing  boards.  The  tripod,  al- 
though a  convenience  for  the  beginner,  is  not  essential.  The 
following  plan  proved  successful  at  the  Plattsburg  Training 
Camps  of  1915:  purchase  a  sufficient  amount  of  soft  pine 
material  12"  by  1"  and  saw  into  boards  about  a  foot  square. 
The  drawing  board  may  be  suspended  around  the  neck  by 

91 


92  MILITARY  SKETCHING 

means  of  a  strong  cord  attached  to  the  sides  of  the  board  in 
such  a  manner  as  to  hold  it  in  a  horizontal  position  at  the 
proper  height  for  sketching. 

COMPASS 

Write  to  the  Keuffel  &  Esser  Cmpany,  or  any  other 
reliable  dealer,  for  samples,  and  select  some  good  round 
compass  that  may  be  set  into  the  drawing  board  by  means  of 
boring  a  hole  of  the  same  diameter  as  the  compass,  and  of  a 
sufficient  depth  to  make  the  top  of  the  compass  flush  with  the 
surface  of  the  board.  By  purchasing  the  compasses  in  lot,  a 
considerable  reduction  may  be  obtained. 

ATTACHMENT  FOR  READING  SLOPES 

With  the  many  duties  incident  to  training  camp  life,  the 
men  will  not  have  the  time  nor  the  paraphernalia  for  construc- 
ing  the  slope  board  attachment.  These  should  be  placed  on 
the  boards  before  the  camp  begins.  (See  Fig.  11.)  The  process 
is  simple,  and  with  the  aid  of  a  few  trained  enlisted  men,  the 
work  can  soon  be  accomplished. 

TRIANGULAR  RULER 

Go  to  some  plaining  mill  and  secure  a  sufficient  number  of 
triangular  rulers  similar  to  one  shown  in  Fig.  2.  Only  the 
plain  triangular  pieces  6  inches  long  need  be  obtained. 

PENCILS,  ERASERS,  THUMB  TACKS,  AND  PAPER 

These  articles  should  all  be  secured  in  advance  by  the  camp 
exchange  officer.  The  Faber  HB  pencil  is  recommended,  or  any 
other  pencil  of  about  the  same  degree  of  hardness.  As  to  the 
paper,  transparent  sheets  may  be  obtained  at  a  reasonable  rate. 
This  class  of  paper  is  of  advantage  as  the  rain  will  not  affect 
it  to  any  great  extent,  and  prints  may  be  made  directly  from 
the  field  sketches;  however,  for  instruction  purposes,  the 
ordinary  sheets  of  drawing  paper  will  answer  the  purpose. 

Do  not  fail  to  have  the  equipment  as  outlined  ready  for  issue 
at  the  first  period  of  instruction  or  previous  to  that  time.  The 
cost  of  the  entire  equipment  as  given  above  will  not  amount  to 


SUGGESTIONS  FOR  INSTRUCTION  AT  TRAINING  CAMPS    93 

much.  The  compass  will  be  the  largest  item,  but,  as  a  matter 
of  fact,  it  is  a  very  essential  part  of  a  soldier's  equipment.  Pos- 
sibly, funds  allotted  for  training  camp  purposes  may  be  avail- 
able, especially  for  the  drawing  boards  and  the  labor  in  con- 
nection with  the  attachment  for  reading  angles  of  slope. 

Do  not  attempt  to  have  several  work  at  the  same  drawing 
board.  The  plan  has  not  proven  successful.  One  or  two 
will  do  the  work  and  the  remaining  men  will  accomplish  little. 
Each  must  do  the  work  individually. 

FIRST  PERIOD 

This  period  may  be  employed  as  follows:  Having  assembled 
the  class  a  conference  may  be  held  involving  the  principles 
outlined  in  Lessons  I  and  II,  also  pointing  out  the  necessity  of 
being  able  to  make  a  sketch  and  read  a  military  map.  Then 
take  the  entire  class  to  the  target  range,  if  one  is  available; 
if  not,  then  to  some  suitable  course  previously  measured, 
and  let  each  man  determine  the  length  of  his  pace  or  stride 
as  described  in  Lesson  I.  When  this  has  been  done,  without 
doubt  the  time  allotted  will  have  been  used  up,  and  the  class 
mat  be  dismissed  with  instructions  to  inscribe  on  their  tri- 
angular ruler,  aided  by  Figs.  2  and  3,  a  working  scale  of  paces 
or  strides  for  3"  equals  one  mile  and  6"  equals  one  mile.  The 
following  text  references  for  the  second  period  should  also  be 
given  out :  Lessons  VI  and  XL  There  will  probably  be  very  little 
time  for  any  preparation,  but  those  who  do  find  a  few  minutes 
to  read  over  the  text  references  for  the  following  day  will  be 
in  a  more  receptive  mood  to  grasp  the  practical  work. 

SECOND  PERIOD 

Explain  by  the  aid  of  the  blackboard  the  following  basic 
principles  of  sketching:  orientation,  distance,  direction,  inter- 
section, resection,  and  conventional  signs.  Students  may 
consult  the  text  freely  regarding  the  latter  until  they  become 
familiar  with  the  various  signs.  Then  assign  some  short, 
irregular  course,  not  over  a  mile  and  a  half  in  length,  and,  if 
practicable,  a  closed  course.  With  a  large  class  it  will  be 
found  better  to  divide  the  class  into  sections,  appointing  such 


94  MILITARY  SKETCHING 

assistants  as  you  may  have  in  charge  of  the  various  sections, 
and  prescribing  several  courses.  Many  members  of  the  camp 
will  be  found  to  be  experienced  engineers,  although  not  familiar 
with  the  hasty  sketching  methods  followed  out  in  the  army. 
Such  men  should  be  distributed  among  the  various  sections, 
as  they  naturally  acquire  a  knowledge  of  the  work  more  readily 
and  will  render  valuable  assistance  in  helping  the  less  fortunate 
over  difficulties. 

THIRD  PERIOD 
Relief  Map  and  Contours 

Before  the  opening  of  the  camp,  secure  a  sufficient  amount 
of  moulder's  wax  and  construct  a  relief  map  similar  to  the 
one  shown  in  Fig.  9,  exhibiting  the  original  map  along  with  the 
relief  map.  These  maps  may  be  displayed  in  a  vertical  and 
elevated  position  at  the  conference,  and  the  nature  and  object 
of  contours  explained  therefrom. 

Following  this  explanation,  mimeographed  copies  of  Fig.  14 
or  some  similar  illustration  should  be  issued  to  the  class,  and 
each  member  should  be  required  to  interpolate  the  contours. 
In  other  words,  impress  on  the  student's  mind  the  importance 
of  first  outlining  the  drainage. 

An  explanation  of  the  auxiliary  scale  of  elevations  shown  in 
Fig.  13  and  its  use  should  be  given.  Each  man  should  place 
this  scale  for  3"  and  6"  equals  one  mile  on  his  triangular  work- 
ing scale.  Fig.  13  is  a  correct  scale  of  elevations  for  3"  equals 
one  mile.  By  using  every  other  division,  a  scale  of  elevations 
for  6"  equals  one  mile  may  be  constructed.  Also  explain  the 
use  of  the  slope-board.  This  entire  period  is  devoted  to 
conference.  Text  reference  for  following  period:  read  over 
Lesson  XII. 

FOURTH  PERIOD 
Road  Sketch 

Pick  out  about  one  and  a  half  miles  of  road,  preferably  with 
as  much  relief  as  possible.  If  practicable,  select  several  routes 
so  that  the  roads  will  not  be  too  congested  with  sketchers. 
Text  reference  for  following  period:  read  over  Lesson  XIII. 


SUGGESTIONS  FOR  INSTRUCTION  AT  TRAINING  CAMPS    95 

FIFTH  PERIOD 
Position  and  Outpost  Sketch 

Select  several  areas  of  about  half  of  a  square  mile,  and 
assign  sections  to  their  tasks,  first  explaining  basic  principles 
as  outlined  in  Lesson  XIII. 

Text  reference  for  following  period :  read  over  Lesson  XIV. 

SIXTH  PERIOD 
Place  Sketch 

Deploy  the  entire  class  along  some  crest,  and  require  each  to 
sketch  a  prescribed  sector,  first  explaining  basic  principles  as 
outlined  in  Lesson  XIV. 

It  was  found  at  the  Plattsburg  Training  Camps  that,  after  a 
course  of  six  periods  as  outlined  above,  nearly  every  man  was 
able  to  turn  in  very  creditable  road,  position,  and  place 
sketches.  Their  idea  of  drainage  was  good,  and,  along  with 
the  practical  work,  they  had  automatically  learned  much 
about  reading  a  military  map. 


LD21-100«.7,'39(402S) 


YC  64477 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


